I had the same problem. The was too much friction due to dirt and lack of lube in the lock. I took the lock out, cleaned with WD40 then lubed with grease and its been working fine since.

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85 300D turbo pristine w 157k when purchased 161K now
83 300 D turbo 297K runs great. SOLD!
83 240D 4 spd manual- parted out then junked