S124300, I was hoping to find a solution before replacing parts. Mostly because I am not sure which part to replace at this point. I will try using the graphite stuff for locks, though it does not feel as if any part of the mechanism is "stuck"

i6h000- I've replaced door straps on this car before. It sure feels like a different issue. When the strap fails the door does not travel smoothly and at times you hear a groaning sound.

This is different in nature. Door travels smoothly & silently - just does not "bite" it does not engage & click when coming in contact with the door striker- therefore not secured to the frame.
So I am wondering whether this is an issue with the door lock or with the striker on the frame.
Thanks for the good thoughts.