Failed to index files / Failed to build cache tree

Hello,

we are working for a customer, using Seafile for some time without problems. But suddenly, one library isn’t syncing. In the logfile the following messages appeareing:

[04/25/18 00:33:08] sync-mgr.c(702): Repo 'Fotos' sync state transition from 'uploading' to 'initializing'.
[04/25/18 00:33:08] sync-mgr.c(1516): Removing blocks for repo Fotos(746495d4).
[04/25/18 04:00:12] sync-mgr.c(702): Repo 'Acmeplan_HD' sync state transition from 'synchronized' to 'committing'.
[04/25/18 04:30:58] cache-tree.c(217): You have both 01 Acmeplan Projekte/St. Gallen/ALM-PRÄ-REM-07-07/Präsentation2007/LangweilerWettbewerbFINAL.key and 01 Acmeplan Projekte/St. Gallen/ALM-PRÄ-REM-07-07/Präsentation2007/LangweilerWettbewerbFINAL.key/.typeAttributes.dict
[04/25/18 04:30:58] repo-mgr.c(4240): Failed to build cache tree[04/25/18 04:30:58] sync-mgr.c(1671): [Sync mgr] Failed to commit to repo Acmeplan_HD(cfd33220).
[04/25/18 04:30:58] sync-mgr.c(764): Repo 'Acmeplan_HD' sync state transition from committing to 'error': 'Failed to index files.'.
[04/25/18 16:00:13] sync-mgr.c(702): Repo 'Acmeplan_HD' sync state transition from 'synchronized' to 'committing'.
[04/25/18 16:38:03] cache-tree.c(217): You have both 01 Acmeplan Projekte/St. Gallen/ALM-PRÄ-REM-07-07/Präsentation2007/LangweilerWettbewerbFINAL.key and 01 Acmeplan Projekte/St. Gallen/ALM-PRÄ-REM-07-07/Präsentation2007/LangweilerWettbewerbFINAL.key/.typeAttributes.dict
[04/25/18 16:38:03] repo-mgr.c(4240): Failed to build cache tree[04/25/18 16:38:04] sync-mgr.c(1671): [Sync mgr] Failed to commit to repo Acmeplan_HD(cfd33220).
[04/25/18 16:38:04] sync-mgr.c(764): Repo 'Acmeplan_HD' sync state transition from committing to 'error': 'Failed to index files.'. 

What can we do here?

Thanks in advance and kind regards,

René

Is this the file, or is the FINAL.key a folder?