I have now installed A604n expansion, power on and got solid grey square on center of the screen and grey vertical stripes on both sides.
After power off and try again display was normal, so it was just one time of that grayish screen.
Firstly i noticed that Indivision video output moved little bit to the left on screen, couple of lines what i adjusted with old expansion unit installed.
I have power on machine many times for now and running with it and it's looking stable with zero graphics issues.
I ordered CA-PSU anyway to protect Amiga for good. I tested powering with re-capped Amiga PSU and its working also with that.
Finally the original memory expansion unit was faulty or doesn't work with my hardware somehow.
I think this issue are now resolved and thanks for help