IF it is stalling then the bit is touching the board LONG before the Current Sensing is turned on... The Current Sensing is what tells the bit that it has touched the board and reverses the direction. SO if the bit is TOO LONG then it will touch the board long before it expects and will be like driving a car into a wall... Something must give..... Shorten the BIT.... OR something to do with the bit not touching the bit Plate and the computer has the tip of the bit WRONG.... Watch the Bit Plate touch too...

AL