Two issues have emerged:
1. POT4 always returns 0, as evidenced from my test project* which plays a big chord using knobs.
2. the two rightmost light-emitting segments do not light up anymore, as evidenced from the getting-started project.

I suspect these resulted from violent separations of Bela from PEPPER. Things have definitely gotten bent.

Using the IDE's pinout diagram I have resoldered for the analog input and those digital pins pd15 and pd16.
Tested the pot itself, seems fine. Resoldered the pot and its adjacent resistor and the leads for the segments.

Any advice on test probes etc that would cast more light appreciated.
Thanks to AIL and @giuliomoro for making this great stuff.

    plate-of-shrimp I suspect these resulted from violent separations of Bela from PEPPER. Things have definitely gotten bent.

    for a violent separation to cause troubles I'd expect the problem to become evident: one or more pins bent out so far that they no longer make contact when the boards are put back together. Can you see anything like that ?

    plate-of-shrimp Tested the pot itself, seems fine. Resoldered the pot

    desoldering the pot may well have damaged some relevant tracks of the PCB ... Do you have the appropriate jumpers in place? Does the corresponding Bela analog in work? What is the exact pot that is giving you trouble?
    The design files for your version may help you troubleshooting https://github.com/BelaPlatform/bela-pepper/tree/master/Design%20Files

    thanks for sharing this. Unsolicited advice on repo management would be to exclude the file pepper-cmaj7plus (as that is the binary built by the IDE/makefile) and all the ._.* (temp files added by sshfs)

          Can you see anything like that ?

          I don't think so, pins can still make their insertions into headers.

          Do you have the appropriate jumpers in place?

          Hmm, I wonder, I may have moved something and forgotten.

          Does the corresponding Bela analog in work?

          Yes, driving the Bela's input via a pot works fine. Whew.
          I have not checked the Bela's digitals directly.

          What is the exact pot that is giving you trouble?

          In terms of looking at PEPPER in the face,
          1 2
          3 4 <- this one
          5 6
          7 8
          I have to become unlazy and actually read the diagrams.

          that is the binary

          Yes, I need to remove that binary, .gitignore was a little stale.