This is a common occurence to the early 140 chassis cars that the rear windows act strange. They usually jerk some up or down and what happens over age is that the sliding jaw cracks and lets the actuating cable slip. The good news is it's easy to replace, the bad is you can only purchase a new regulator assembly as the jaw is not available. You could on the earlier 126 cars but not the 140! To look inside the door panel you have to remove the flat wood panel by the window switch. This can be done with a feeler gauge by sliding it on the rear edge of the panel and flipping the catches up that retains it. There are two catches on the back of the panel that face the rear of the door. Once this is off the rest is easy as with a normal door panel. The regulator usually has large rivets to mount it but I've used #8 or #10 aircraft bolts to replace them as a hydraulic pop rivet gun is needed for the factory rivets and I don't own one! With bolts, another assembly can be replaced again more easily.
Can't help you with the right front door, maybe a switch is bad?