Take a look at
I’m no expert on this but, apparently, the client can get into “Paused”. When that happens it seems that UrBackup reports a transfer speed of 50 KBit/s.
Why does it get into Pause? and, when it is paused, why does it show 50 KBit/s implying that there is active traffic between client-server?
I have no answer to those questions but it is worth checking if you client is “paused”.