It is possible that the lock is getting old and balky. Using a lubricant is the best thing you could have done. Swapping lock cylinders is not fun, they are put in using break off bolts, so there is no head to turn.

There are documented procedures to remove and replace with one ordered from the factory, through a dealer. Drilling out the bolt is tedious, but I like the one write up I found that drils a small dent in the outer edge of the bolt and then just uses a tap and hammer to turn the bolt counter clockwise. Once started, the old bolt comes out easily.

Klaus
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There is no present time, just the past and future