big volume drop with interactive volumes

[d95err]

the switch part on Normal 1 was bad: without a plug the switch wasn't closed. Could this cause the issues I'm having?

Any noise generated at the ungrounded unused input will be amplified and fed back through that channel. I don't know if this is the cause of your problems, but it should account for at least some unnecessary noise in the amp.

[koen]

I got my new jack installed, it still drops the volume a lot between 10 and 12.

'The voltages on pin 2 and 7 on V1 are always 0, with any settings on the volume pots.'
How about V2?

Same as posted a few days ago, no change when turning the pots.