i really dont know

It appears that differential isn't being driven properly, general rule of thumb with differentials is that you have 1 input and two outputs or alternatively 2 inputs and one output. When it comes to driving vehicles generally the differential case is the input and the gear set inside of it is for the outputs.

I did this on some of my old pumps, it didn't actually help. You can check by putting the bottom of the pump in a container of water, the air inlet is through the top. Might have helped if I prepped the surface a bit better though.

to my understanding the only likely reason this would happen with the motors is if they were under significant load for a sustained time (like stall conditions) that would cause the motors to heat up quickly and potentially cause damage.

I've been thinking about messing around with some grease in my pneumatic cylinders, in particular my small cylinders which have a lot of "sticktion" when operating which means they only work at higher pressures which is problematic. It sounds like the "sticktion" with the molykote 111 is pretty low? is that a correct assessment? Guess I'll have a look around and see if i can get my hands on some of that grease and try it out myself, I'll try to remember to report my results when i get around to it. :)

I know I personally have a handful of these preordered already. I'm excited to get my hands on them, gonna have to make a custom power supply to deal with the current demands of the motors however.