What would cause 1993 Lincoln Cartier clock lose time?

First of all every clock or watch with mechanical mechanism has to be serviced every 3 or 4 years. Your clock is too old to go problem free without any tune-up.

If you mechanical mechanism is loosing time it means that there is a problem with its mainspring. Most likely it got magnetized from sitting on top of TV or speaker. It is a very simple procedure to get it demagnetized.

Good luck.

W-Precision