LDAP user sync stuck with "Synchronization ignored as it's already in progress"

Hi
keycloak noob question… where i was not able to find a solution…

i use keycloak 12.0.1 with 1 main and 2 followers. I have set up a LDAP User Federation to our AD. it used to sync users several times, but now suddenly stopped after the main crashed during a sync (for unknown reason). i now only get “Success! Sync of users finished successfully. Synchronization ignored as it’s already in progress” when clicking on “Synchronize all users”.

i restartet my main and tried different things… still stuck.
from debug log i see:

[Server:server-one] 11:42:23,315 DEBUG [org.keycloak.services.resources.admin.UserStorageProviderResource] (default task-5) Syncing users
[Server:server-one] 11:42:23,316 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) new JtaTransactionWrapper
[Server:server-one] 11:42:23,316 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) was existing? true
[Server:server-one] 11:42:23,317 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) JtaTransactionWrapper  commit
[Server:server-one] 11:42:23,317 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) JtaTransactionWrapper end
[Server:server-one] 11:42:23,317 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) JtaTransactionWrapper resuming suspended
[Server:server-one] 11:42:23,317 DEBUG [org.keycloak.services.managers.UserStorageSyncManager] (default task-5) syncAllUsers for federation provider FOO was ignored as it's already in progress
[Server:server-one] 11:42:23,320 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) JtaTransactionWrapper  commit
[Server:server-one] 11:42:23,327 DEBUG [org.keycloak.transaction.JtaTransactionWrapper] (default task-5) JtaTransactionWrapper end
[Server:server-one] 11:42:23,327 DEBUG [org.keycloak.events] (default task-5) operationType=ACTION, realmId=master, clientId=****, userId=****, ipAddress=****, resourceType=REALM, resourcePath=user-storage/***/sync

how am i supposed to remove that “in progress” sync job? where can i get more infos about that job if it really is doing something useful?

thanx a lot and greets, ivo

i even removed the realm and re-created it from export. still stuck…

seems it recoverd somewhen. not sure what i did, as i did a lot. deactivating that User Federation for hours, removed completely all users, …