You may not get the full use of your batteries, see my post above and the link s in it which explain why, it’s related to the battery voltage of NiMH batteries which are lower than Alkaline and Lithium 1.5v so the circuit shuts down faster, depending on the voltage and load put on your NiMH batteries. When the motor runs it puts a heavy load on the batteries and if the battery can’t supply it the voltage tanks and it shuts off the circuit to the lock.
REF, for a steady state small current draw voltage curve:
Under heavy load the voltage will drop faster for lower quality batteries.