Sometimes an offset screwdriver is the right tool for the job. They take some getting used to, but can work where others won't.

Did you strip the screw or plastic it was screwed into?

I was removing part of the bobbin "stuff" on a singer 646. I got the black screw out perfectly. (I borrowed my Dh's Chapman screw driver set. ) The (apparent) aluminum screw on the next level would not move. So, thought, well, maybe it's one of those backwards screws. It moved about a 1/4 turn, but then it stuck. I tried it again the other way, but it moved 1/4 turn and stuck again. I had to work today and got home late, so I'm not sure what the Pb blaster did to it. I'll try again tomorrow.
bkay