Decrease electromagnet discharge time
The electromagnets are only turned off.


To get rid of the remnant magnetic field you should reduce the current using a decaying alternating current. The idea is to reduce the magnetic field by forcing it through a curve like this:



This is an example current waveform which does this:



You might have to experiment with how long and how fast a decay you can get away with.
Just reversing the current for a short period might be enough.

(I realize that this requires significant more logic then just an off switch).

Both images where taken from http://meettechniek.info/passive/magnetic-hysteresis.html