Hi All,
I solved the problem ... very simple, actually silly.
The ACR window always opened so tight to the upper edge of the monitor that the upper frame edge was not visable ... therefore nothing to grab on with the cursor ... and me being unaware.
Luckily, after open/close many times at one time a small sliver of the upper frame was visible and I could grab it and move to the other monitor where it now opens always at set size, placement, etc.
Glad it was a simple problem and hope it might ease some possible frustration in case someone exerienses the same.
Cheers
thanks for that, @Tele55