Broken Door Lock Driver Side, 318i

[SquireOne]

When you push on the door lock it will not go down, it will not lock. Attempting to lock from the outside with a key revealed the lock outside spins sort of loosely, and sorta pops past the locking point. In other words, key doesn't work either. What is the solution? Buy a new lock? I haven't taken the door panel off yet to look at the lock assembly. Is this a hard problem to fix? Anybody else experience this problem? Thanks!

Edit: This is a 1985 318i

[85-325e]

The exact same thing happened to me, but only when it was really cold outside. A friend of mine told me to lubricate the locks. I wasn't exactly sure what he meant and I never did. As the weather warmed up it fixed itself. My car is also from 1985. Is yours a problem in the cold or is it consistently this way?