Strange Wiring Problem

Confirm that you only have the starter interlock circuit going through that clutch switch. It almost sounds like you have part of an operating system (sourced from the ignition, etc) running through that switch instead. When you push the clutch, it closes the switch and completes the circuit (so the thing would work normal). But when you let off the clutch, the switch opens and the circuit cant function properly.
I know that is kind of a weird suggestion, but it should take all of 30 seconds to check out.

Good luck.

Seeing what the code your getting is a good idea too.

Good luck.

Find the clutch safety switch (on the back of the clutch pedal). There are two connectors (one for the starter circuit and one for CC). IIRC, the correct wiring connector has two terminals. One has two wires in one slot and and one wire in another slot.

I would check your wiring colors going to and leaving that switch to make sure they are correct. Make sure that one side of that connector gets 12 volts only when cranking.

This is all not super likely, but was worth mentioning. Otherwise, I would be chasing the circuits that were rewired with my meter. Look for something other than the starter interlock circuit that changes values simply from having the clutch pedal depressed vs not (other than CC, there should be almost nothing).

Good luck.