I was trying to open up the window motor of my 83 300sd. I got one of the hex screws off without issues. The other one was very stubborn and partly due to frustration, I ended up rounding it off. It is one of those hex key screws. I don't know why they even bother to use those things. How can I unscrew it or just remove it one way or the other. thanks for any help.

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W126 1983 300SD 286,000 miles and ticking
Baby blue exterior Grey MB tex
Recent work:
Replaced air cleaner mounting brackets and heat shields
Replaced alternator, fan and power steering belts
Replaced positive battery terminal
Replaced negative battery terminal and cord
New Duralast Battery

My car needs work.