I tried to check the logfile, but failed. Now my RUMBA-board is broken. I touched a metal part with a cable, have seen a spark and need now some time to fix it :-( .
Therefore I cannot send anything right now.
I found in another, older topic, that even with unplugged servo I had those restarts.
It is a rotating servo having a small motor, the load is equal for on/off because of the rotation-symmetry.
I will send the logfile as soon I have rebuild everything. Maybe it will not happen using the Rumba+ board, which I ordered.
Thanks so far for your help!