Why servo is sticking?
 

Hello,
I have a small automated machine with actuator an MG90S servo motor.
Ever since I've had this machine, this servo has stopped working regularly.
Its power supply has been checked multiple times and is a constant 4.9V
PWM signal arrives as it is in characteristics and as expected.
It's just that the servo itself stops. By replacing it with a new one and everything starts working normally, until next time.
And the next time is after 1-2 to 3 days maximum. The servo makes 2000-4000 cycles per hour, from 5 degrees to 35 degrees of rotation. The load it lifts is about 50 grams. The load is attached to a sliding rail and is regularly lubricated, so the mechanism is not sticking. The gears are good, I have looked at them on several times and I can't find anything suspicious.
Please, if anyone knows, explain why the servo motor stops suddenly. It's just that it has little life, or we're doing something wrong.
Please, recommend me a stronger servo motor with similar dimensions.

Well, first a small hint:

while

As for your question... as far as I can see, the MG90S is a tiny little micro servo and 2000-400 cycles per hour translates to about once per second. Non-stop over several days, if i understand correctly? My guess would be that it's just not made for this type of use. Does it have to be such a tiny unit?

It is a 5 dollar servo, replace it. It is just cheap quality

Replacing servo is not too easy-must de-assembly machine.

Maybe this will help: Servo Database - RC Servo Specs and Reviews

Thank you very much, I will check that.