For the non engineers people
In section 1.2.3 of "the robot", the mentioned that the seat motor have a Positive temperature coefficient (PTC) thermistor for over load protection. But actually, window motor and Van door have them too. The PTC device will reduce motor current and output torque as heat increases.
If you motors are heating up, try reducing side loads on the mechanism, use a bigger gear ratio to reduce the load on the motor, and reduce the internal friction of the device. Stalling out motors is one of the major ways to heat up motor. Competition usage and the temperature around the motor also add to that too.
You want to watch out for the windows motors, especially this year's because of their lower max power output. Do some calculation and see if these window motors satisfy how much torque your mechanism need while finishing the task with the speed you want.
If you find out that you demand a certain speed from these guys, and they are stalling out while doing the job... I suggest you get more powerful motors to do the job.