CLient connection problem after upgrade to 2.5.27

Hello everybody,
after upgrading the server from 2.4.14 to 2.5.27 some clients do not connect to the server. More precisely, the client connects to the server for a few seconds and then disconnects: how can I fix it?

activate debug log on client… Clients are 2.4…? or updated

the clients updated automatically and without any problems to version 2.5.21.
They connect for a few seconds and then disconnect.
I didn’t find anything in the log, if you want I’ll send it to you, but in the end I found a practical solution.
I’ll explain.
I have two operating offices each with about ten computers, all saved on a windows11 computer with urbackup.
I have always updated the various versions without problems.
With this update in both the first site and the second site, a couple of computers could no longer connect to the server.
After several tests I found a practical solution.
I deleted the machines that didn’t connect from the console, then I stopped the server service on the master machine, renamed the backup folders (so as not to lose the old backups), and launched the manual cleanup command (cleanup.bat)
When the service restarted, the deleted clients reconnected and everything started regularly.