I have a 2000 corolla and both rear windows have the same problem.
They will roll down but only halfway up before quitting.  If I wait a
minute they will finish rolling up.  I thought they might be binding on
something so I removed the motors and tried them removed from the
regulator.  If I activate the motor it will run for about 15 seconds
then slow down and stop as if the battery went dead.  I opened the
motor and cleaned with contact cleaner, same result.  If the motors
were wearing out I would expect the front ones to go because they are
used everyday, rears ones hardly ever, any ideas?