By the way, I am working on your 4.7k resistor suggestion at this exact moment, so I will see if that works before getting into transistors, etc.
The physical stop of the mechanism to which the servo is attached.The physical stop in this case is actually a microswitch that,
A better mechanical design would allow the mechanism to move past the limit switch without causing damage.
Alternatively the limit switch should just cut off the power to the motor (independently of the Arduino) so there is no possibility of it causing damage....R
This servo carries meso-position adjustment potentiometer(it can only be seen by peeling off the outer cover and circuit board). We can set high level pulse at 1.5ms to observe that whether servo stops rotating. If it doesn't stop rotating, we keep adjusting the potentiometer until it does.
Did you try this?