I was able to reproduce this behavior. I created Ram disk (R:\) and launched PH from it's root folder. So, what i get:
Image file name: \Device\ImDisk0\ProcessHacker.exe
Command line: "R:\ProcessHacker.exe"
I figured that Process Hacker tries to find plugins in "R:\Device\ImDisk0\plugins\"
. It combines image file name, drive, and \plugins\
sub-folder. And it fails.
I was not able to force windows to use "R:\ProcessHacker.exe"
as image file name. For you it's easier to put plugins in the place, where PH searches for them. It will work