Hi,
problem is solved from my end, thanks for offering help. I changed plans and went for a complete re-install instead of trying to fix the old one. Having read that this can be shortened dramatically by just kicking-off the new installation process, and then cancel and just copy over the OneStore directory, I tried this and it worked perfectly - complete re-install and back in the air in less than an hour (not counting the copy-time for the 120GB OneStore-files to the new SDD which I did before).
So we can close this from my perspective, would still be interesting to know though why the “Move” command did not do its job here. Maybe it only works well when using the standard installation paths on C:.…