Before we upgraded our Routers to 6.25 everything works perfectly, but now the bandwith-test only works in tcp-mode.
In udp-mode they are both connected, i see the session on the bandwith-test-server, and on the client is says "running" but
there are no packets generated, the graph still stays on 0bps. Is there anyone else experiencing the same problem?
As I said before, in tcp-mode everything is working perfectly. There are no firewall filterrules on both client and server.

Please upgrade your MikroTik RouterOS to 6.27, let us know how bandwidth server works there.

I can confirm, with 6.27 it is working now! maybe a bug in 6.25?