fatdoggy - sorry forgot to reply on a couple of points from your checklist.
motor run-in
I've gone two packs half throttle max. the started to push it more and more. Probably not ideal, but that's the vest I copuld do at that time.
Motor binding
I took it apart and expected all inside but didn't find anything suspicious.
Brush hoods
Inspected them as well, but don't see any problem with them.
Is there any way how to test the arm whether it's shorted?
Thanks again