Z Axis Losing Position/Drifting on Long Carves after installing Z 20 Motor/Brake option

Since I have installed the Z-20 Motor/Brake option on long 12 hour carves I began having issue with Z axis drifting down linearly and consistently. On 6 carves of same picture Z shifted down exactly .180.

I did tests running same program with spindle and dust collector powered down and the Z still drifted .180.

Next I replaced the Z-20 Motor having the brake with the original motor and ran the program again. This time Z axis held position as expected.

Anyone else experience similar issues?