Poorness,
Good troubleshooting!
You possibly have a bad pot, but there’s also a good chance that the problem is something else, like the microcontroller is injecting 5V on the pot…you just don’t notice it until there is enough resistance on the pot to hold it above ground level.
Test the pot by measuring the resistance of the microcontroller’s pin 24 to ground, when the pedal power is off. It should scale from around 0 ohms to around 100k ohms as you turn it. If it’s is stuck at some high value for most of the rotation then the pot’s bad.
If the pot’s good then remove the microcontroller from it’s socket (very carefully, without bending it’s pins) and power up the pedal…then measure the voltage on pin 24 again as you rotate the rate pot. Test to see if the voltage is scaling as you rotate it. If this works, then the problem is with the microcontroller…or there’s somehow a short between pin 24 and 5V.
Let me know what you find.
-Brach