Sever the marked connections on the circuit board (scratching with a screwdriver should be sufficient)

Unsolder the marked components from the circuit board (keep zener diodes XX and YY or have equivalent components handy)

Connect the points 1 through XX with wires (I tried to keep them short and flush with the circuit board, so they would not interfere with the casing)

Add the capacitor to protect the circuit from the motor

Add the Zener diode