Error while enumerating user "NT AUTHORITY\SYSTEM" groups: 2453

Hello everyone. I hope someone can help me, I can’t understand where I’m wrong.
I’m having this problem:
urbackup works beautifully on all computers on the network, I am trying to do the same thing on a server that has a different class. The urbackup server is on 192.168.2.XXX.
All the PCs are on + one pc (windows server) is on
When I install the client on the server pc, it works and the first backup is completed without problems, then, client / server lose the connection and are never found again! In the client logs I read this:

2020-03-02 13:56:53: WARNING: Info not found at 'c:' - reindexing

2020-03-02 13:57:13: WARNING: Info not found at 'd:' - reindexing

2020-03-02 14:10:29: ERROR: Error while enumerating user "NT AUTHORITY \ SYSTEM" groups: 2453

2020-03-02 14:43:49: ERROR: Indexing interrupted by configuration change

2020-03-02 14:43:57: ERROR: Not found

2020-03-02 14:43:58: ERROR: Not found