Door lock help, Doesn't work 100% Options

[screenguy914]

Need assistance with my passenger door before I tear into the door.

Able to lock/unlock from the inside and outside with the key
Interior and exterior door release handles operate

However, when locking with the key, it rotates only about 10 degrees, then stops. I should be satisfied, but I fear it might get worse.

Is this an issue with the key tumbler or with the exterior door handle mechanism?

Thanks

[mepstein]

Every tumbler I have taken apart is gummed up. Actually, every latch, lock, pull, winder, cable, etc is gummed up on these cars after 50 years. The best thing to do is clean and lube each part with a dry lube. 2nd best is to just lube it as a temporary measure until you can clean and lube properly.

The harder it is to operate, the more wear and tear you put on the parts.