Not real sure if it is the same basic mechanism as the early 90's, but I know that a number of FoMoCo products ate lock modules like candy. If the design has changed in the last decade, then apologies in advance for the rabit trail...
I finally decided on the Mustang that it was easier not to replace the lock than to tear the door apart to get at it.
When they both failed, it was a gradual thing. I believe it was a combination of design and binding from dirt that contributed to the problems.
