Debian Server stops processing data overnight

I have a VM running Debian Bookworm with UrBackup storing client data on a TrueNAS Mini-R mounted over NFS. However, starting at around between 4 and 5 am, all client backups fail. Could it be due to the NFS mount? I can switch to iSCSI if needed although I’d prefer not to. Restarting the server service fixes it for the day, but that is not a valid solution.