Yep, using the troubleshooting guide, as well as the schematic in the assembly guide (both of which are incredibly helpful, you guys are amazing).
I’m not usually one to buy in to superstition around unlucky numbers… but…
I traced the ‘always-on’ regardless of bypass switch/LED back to pin ***13*** (i.e. RLY2) on the microcontroller. It looks like the connection must be shorted in some way to pin 14; a continuity test shows both pins are connected to R31, instead of R32 and R31 respectively.
As to the lack of audio and bad opamp voltages… it looks like the solder joint on pin ***13*** (i.e. opamp D, V-) on the opamp IC isn’t connected; the pad is reading 4.5V (well, 4.7V) but the pin itself is reading 1.5V… which is likely then screwing up the values of opamp C downstream.
Pin 13 on the microcontroller… pin 13 on the quad opamp… jeez. I’ll break out the soldering iron later and see if that does it.