Mosfet motor problems with bluetooth module
The regulator has an internal current limiter which is close to your average motor current.  A motor does not draw a constant current but has a "current ripple", so it is possible that the current ripple is hitting its peak and dropping the output voltage accordingly.  Look at the motor voltage with a scope and see if it is being pulled low periodically with the brushes.  The occasional shutdown might occur either from the regulator dropping too low and pulling down your controller or possibly the thermal limit being reached.  Something to try might be to run your controller from the regulator but run the motor/FET circuit directly from your benchtop supply.  This might be better practice so that motor back EMF will not create high voltage on your controller.