Sometimes solder joints go bad in the box. It can be opened up but the circuit board is covered with a compound that's difficult to remove. Once removed, you can try to resolder to see if that fixes it.
If not, replace with used OEM parts, or new, or aftermarket, or buy an ignititech ignition system and eliminate the controller and use the ignition to control the servo.....or a double pole double throw switch can wired in place of the controller so you can set v boost wide open or closed depending on the situation.
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