I started getting loud crackling sounds so opened the pedal up again as clearly there was still a bad joint.
Redid all the soldering again.
I then 'rocked it out of the box' - which is easy to do with Aion's style of offboard wiring. However, I spent over an hour trying to debug a 'signal when off but no signal when on' problem before I realized that the pedal works best if you plug the input into the Input, and the output into the Output.
Another lesson learned from build #1....