Backups are stalling

First, my setup:

Server - Windows 10 22H2 / Urbackup Server 2.5.31
Client - Windows Server 2019 / Urbackup Client 2.5.24

And now my problem:

When backing up files on several clients, the process stalls and the ETA goes to a very long time, often several years. In the log, it’s in a loop repeating something like this:

07/28/23 09:21 DEBUG Waiting for metadata download stream to finish (attempt 35284, XXX). 4 days 3h 6m 24s since last meta-data transfer. Forcefully shutting down after 2m 20s without transfer.
07/28/23 09:21 DEBUG No meta-data transfer in the last 4 days 3h 6m 24s. Shutting down meta-data tranfer.