The good news. The switch surgery fixed the calibration block. It made sense since it was the rudder switch and the rudder sweep on the pot that was blocking the calibration. The switch was likely in the wrong position.
Bad news. We studiously followed the guidance on a website. Conferred amongst ourselves, quadruple checked and got it wrong. Will need to tear the quad down, cut off heat shrink, re-wire etc. as the motors turned the wrong way – you can work this out because when you throttle up after calibration (with props of course) your lock nuts fly off, straight up, bounce of ceiling, land in you beer. If they don’t land in you beer, keep trying until they do land in your beer.
Although the beer might, I say might, actually be the root cause … just saying.
All part of the learning process.