NC Client can't sync, because of missing file


my NC Client can’t generally sync, because of a missing file which was linked in NC over federated cloud id. The file is definitly is not in NC but the link existing in the webinterface and it shows as existing file.

NC client shows error “503 Service Unavailable” on “GET …[domain/path]…” + filename

For this reason I scan with:
sudo -u www-data php occ files:scan --all

But it doesn’t work.
How can I solve this, maybe in the database?

Nextcloud version: 16.0.8
Operating system and version: Ubuntu 18.04 LTS
Apache version: Apache 2.4.29
PHP version: 7.2