diff --git a/src/agenda_culturel/celery.py b/src/agenda_culturel/celery.py
index ce23b7b..05b888a 100644
--- a/src/agenda_culturel/celery.py
+++ b/src/agenda_culturel/celery.py
@@ -4,6 +4,10 @@ import json
 from celery import Celery, Task
 from celery.schedules import crontab
 from celery.utils.log import get_task_logger
+import time as time_
+
+
+from contextlib import contextmanager
 
 from .import_tasks.downloader import *
 from .import_tasks.extractor import *
@@ -18,6 +22,8 @@ os.environ.setdefault("DJANGO_SETTINGS_MODULE", f"agenda_culturel.settings.{APP_
 
 app = Celery("agenda_culturel")
 
+from django.core.cache import cache
+
 logger = get_task_logger(__name__)
 
 
@@ -30,6 +36,26 @@ app.config_from_object("django.conf:settings", namespace="CELERY")
 # Load task modules from all registered Django apps.
 app.autodiscover_tasks()
 
+LOCK_EXPIRE = 60 * 10  # Lock expires in 10 minutes
+
+@contextmanager
+def memcache_chromium_lock(oid):
+    lock_id = "chromium-lock"
+    timeout_at = time_.monotonic() + LOCK_EXPIRE - 3
+    # cache.add fails if the key already exists
+    status = cache.add(lock_id, oid, LOCK_EXPIRE)
+    try:
+        yield status
+    finally:
+        # memcache delete is very slow, but we have to use it to take
+        # advantage of using add() for atomic locking
+        if time_.monotonic() < timeout_at and status:
+            # don't release the lock if we exceeded the timeout
+            # to lessen the chance of releasing an expired lock
+            # owned by someone else
+            # also don't release the lock if we didn't acquire it
+            cache.delete(lock_id)
+
 
 def close_import_task(taskid, success, error_message, importer):
     from agenda_culturel.models import BatchImportation
@@ -84,33 +110,21 @@ class ChromiumTask(Task):
         return self._chm
 
 
-@app.task(base=ChromiumTask, bind=True)
-def run_recurrent_import(self, pk):
+def run_recurrent_import_internal(rimport, downloader, req_id):
     from agenda_culturel.models import RecurrentImport, BatchImportation
     from .db_importer import DBImporterEvents
 
-    logger.info("Run recurrent import: {}".format(self.request.id))
+    logger.info("Run recurrent import: {}".format(req_id))
 
-    # get the recurrent import
-    rimport = RecurrentImport.objects.get(pk=pk)
 
     # create a batch importation
-    importation = BatchImportation(recurrentImport=rimport, celery_id=self.request.id)
+    importation = BatchImportation(recurrentImport=rimport, celery_id=req_id)
     # save batch importation
     importation.save()
 
     # create an importer
-    importer = DBImporterEvents(self.request.id)
+    importer = DBImporterEvents(req_id)
 
-    # prepare downloading and extracting processes
-    if rimport.downloader == RecurrentImport.DOWNLOADER.SIMPLE:
-        downloader = SimpleDownloader()
-    elif rimport.downloader == RecurrentImport.DOWNLOADER.CHROMIUMHEADLESS:
-        downloader = self.chromiumDownloader
-        downloader.pause = False
-    else:
-        downloader = self.chromiumDownloader
-        downloader.pause = True
     
     if rimport.processor == RecurrentImport.PROCESSOR.ICAL:
         extractor = ICALExtractor()
@@ -164,10 +178,44 @@ def run_recurrent_import(self, pk):
         success, error_message = importer.import_events(json_events)
 
         # finally, close task
-        close_import_task(self.request.id, success, error_message, importer)
+        close_import_task(req_id, success, error_message, importer)
     except Exception as e:
         logger.error(e)
-        close_import_task(self.request.id, False, e, importer)
+        close_import_task(req_id, False, e, importer)
+
+    return
+
+
+@app.task(base=ChromiumTask, bind=True)
+def run_recurrent_import(self, pk):
+    from agenda_culturel.models import RecurrentImport
+
+    # get the recurrent import
+    rimport = RecurrentImport.objects.get(pk=pk)
+
+    # prepare downloading and extracting processes
+    if rimport.downloader == RecurrentImport.DOWNLOADER.SIMPLE:
+        downloader = SimpleDownloader()
+    elif rimport.downloader == RecurrentImport.DOWNLOADER.CHROMIUMHEADLESS:
+        downloader = self.chromiumDownloader
+        downloader.pause = False
+    else:
+        downloader = self.chromiumDownloader
+        downloader.pause = True
+
+    # only one thread using Chromium can run at a time,
+    # to prevent from errors (including strange Facebook errors)
+    if rimport.downloader in [RecurrentImport.DOWNLOADER.CHROMIUMHEADLESS, RecurrentImport.DOWNLOADER.CHROMIUMHEADLESSPAUSE]:
+        with memcache_chromium_lock(self.app.oid) as acquired:
+            if acquired:
+                return run_recurrent_import_internal(rimport, downloader, self.request.id)
+    else:
+        return run_recurrent_import_internal(rimport, downloader, self.request.id)
+
+    # if chromium is locked, we wait 30 seconds before retrying
+    raise self.retry(countdown=30)
+
+
 
 
 @app.task(bind=True)
@@ -224,53 +272,61 @@ def import_events_from_url(self, url, cat):
     from agenda_culturel.models import RecurrentImport, BatchImportation
     from agenda_culturel.models import Event, Category
 
-
-    logger.info("URL import: {}".format(self.request.id))
+    with memcache_chromium_lock(self.app.oid) as acquired:
+        if acquired:
 
 
-    # clean url
-    url = Extractor.clean_url(url)
+            logger.info("URL import: {}".format(self.request.id))
 
-    # we check if the url is known
-    existing = Event.objects.filter(uuids__contains=[url])
-    # if it's unknown
-    if len(existing) == 0:
 
-        # create an importer
-        importer = DBImporterEvents(self.request.id)
+            # clean url
+            url = Extractor.clean_url(url)
 
-        # create a batch importation
-        importation = BatchImportation(url_source=url, celery_id=self.request.id)
-        # save batch importation
-        importation.save()
+            # we check if the url is known
+            existing = Event.objects.filter(uuids__contains=[url])
+            # if it's unknown
+            if len(existing) == 0:
 
-        try:
-            ## create loader
-            u2e = URL2Events(ChromiumHeadlessDownloader(), single_event=True)
-            # set default values
-            values = {}
-            if cat is not None:
-                values = {"category": cat}
+                # create an importer
+                importer = DBImporterEvents(self.request.id)
 
-            # get event
-            events = u2e.process(
-                url, published=False, default_values=values
-            )
+                # create a batch importation
+                importation = BatchImportation(url_source=url, celery_id=self.request.id)
+                # save batch importation
+                importation.save()
 
-            if events:
-                # convert it to json
-                json_events = json.dumps(events, default=str)
+                try:
+                    ## create loader
+                    u2e = URL2Events(ChromiumHeadlessDownloader(), single_event=True)
+                    # set default values
+                    values = {}
+                    if cat is not None:
+                        values = {"category": cat}
 
-                # import events (from json)
-                success, error_message = importer.import_events(json_events)
+                    # get event
+                    events = u2e.process(
+                        url, published=False, default_values=values
+                    )
 
-                # finally, close task
-                close_import_task(self.request.id, success, error_message, importer)
-            else:
-                close_import_task(self.request.id, False, "Cannot find any event", importer)
-        except Exception as e:
-            logger.error(e)
-            close_import_task(self.request.id, False, e, importer)
+                    if events:
+                        # convert it to json
+                        json_events = json.dumps(events, default=str)
+
+                        # import events (from json)
+                        success, error_message = importer.import_events(json_events)
+
+                        # finally, close task
+                        close_import_task(self.request.id, success, error_message, importer)
+                    else:
+                        close_import_task(self.request.id, False, "Cannot find any event", importer)
+                except Exception as e:
+                    logger.error(e)
+                    close_import_task(self.request.id, False, e, importer)
+
+            return
+        
+    # if chromium is locked, we wait 30 seconds before retrying
+    raise self.retry(countdown=30)
 
 
 @app.task(base=ChromiumTask, bind=True)
diff --git a/src/agenda_culturel/templates/agenda_culturel/rimports.html b/src/agenda_culturel/templates/agenda_culturel/rimports.html
index 366f1b6..185399a 100644
--- a/src/agenda_culturel/templates/agenda_culturel/rimports.html
+++ b/src/agenda_culturel/templates/agenda_culturel/rimports.html
@@ -3,6 +3,7 @@
 {% block title %}{% block og_title %}Importations récurrentes{% endblock %}{% endblock %}
 
 {% load utils_extra %}
+{% load rimports_extra %}
 {% load cat_extra %}
 {% block entete_header %}
     {% css_categories %}
@@ -13,8 +14,10 @@
 <article>
     <header>
         <div class="slide-buttons">
-            <a href="{% url 'run_all_rimports' %}" role="button">Importer tout {% picto_from_name "play-circle" %}</a>
-            <a href="{% url 'run_all_rimports_failed' %}" role="button">Relancer les imports échoués  {% picto_from_name "play-circle" %}</a>
+            <a href="{% url 'run_all_rimports' %}" role="button">Exécuter tout {% picto_from_name "play-circle" %}</a>
+            {% if has_failed_rimports %}
+            <a href="{% url 'run_all_rimports_failed' %}" role="button">Relancer les imports échoués {% picto_from_name "play-circle" %}</a>
+            {% endif %}
             <a href="{% url 'add_rimport'%}" role="button">Ajouter {% picto_from_name "plus-circle" %}</a>
         </div>
         <h1>Importations récurrentes</h1>
diff --git a/src/agenda_culturel/templatetags/rimports_extra.py b/src/agenda_culturel/templatetags/rimports_extra.py
index fa8aa59..b64829e 100644
--- a/src/agenda_culturel/templatetags/rimports_extra.py
+++ b/src/agenda_culturel/templatetags/rimports_extra.py
@@ -12,6 +12,10 @@ from .utils_extra import picto_from_name
 register = template.Library()
 
 
+@register.simple_tag
+def has_failed_rimports():
+    return BatchImportation.objects.filter(status=BatchImportation.STATUS.FAILED).count() != 0
+
 @register.simple_tag
 def show_badge_failed_rimports(placement="top"):
     newest = BatchImportation.objects.filter(recurrentImport=OuterRef("pk")).order_by(