Ok, did a last try before the weekend anyway. I stumble in to the same problem, and it’s that my Powershell 7 don’t work at all in psu. No real explanation why, it just doesn’t seem to start. Tried upgrading PS7 on the server to latest version, but to no avail. If I try to start a terminal (using automation->terminals) with Powershell 7 it just says “Request failed with status code 500” 
Integrated and Powershell 5 environments work just fine… Also starting Powershell 7 directly on the server using the same path as in the environment setting works without problem…
edit: Also dug through every log file I can find. No explanation. Guess I’ll roll back to snapshot once again for the weekend…