It seems what I've figured out what's gone wrong with new PCB For the reason, I use transistor to cut off connection between coil and power supply, ground is connected permanently and control circuit tracks current on electromagnet to choose duty cycle properly.
That's why transistor works like common-drain-amplifier. Drain current derives from difference between gate-voltage and drain-voltage multiplied by forward transconductance of a transistor, so drain voltage cannot be greater than gate voltage minus voltage drop on gate-drain junction, that's why you can see something like this:
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