Sticking Door Handle Buttons

Hey Everyone,
I have a 1972 Dart Custom Sedan with all of the the factory original locks and keys. Everything is working, but almost every exterior door button gets stuck in the 'in' position from time to time. I searched for thread on this but didn't see a fix.. I would prefer not to remove the mechanisms if possible, but I will be removing the door panels next weekend for an interior restoration, so I can also access the back of the mechanism.

I'm sure this is a simple fix, but any advice on the best lubricant/technique to use for a long term fix would be appreciated..