During switching between guitars with active electronics my petal suddenly lost the sound (LEDs were OK).
I checked and I found that at some tiny moment when you unplug the cable - there is +9V (and even +18V from my bass) on the signal lead. Both guitars I have, stock.
MCP6004 operational amp has shorted the signal to the ground internally.
Temporary fixed with another op amp.
I know that the problem is on my side, just warning you all that this might happen.
Don’t know how to avoid this atm.