O.K., retested some Prime95 & wPrime 1024M and it is definitely has to do with temps !
A few days ago I had my case all open and my temps were about 10c lower than now when my case is closed.
As I said, the temps were about 60-65c @ 4200Mhz and the multi was up to x21 all the time.

From what I see now:
At the beginning of the bench, while the temps are raising, the multi is x21.



After a few seconds the temps go above ~70c and the multi drops to x20.5



Sometimes it even drops to x20 with Prime 95 and jumps between x20.5-x20.



my oah my, why did I close up my case