I have the same issue. It is the same issue that I had with my PFR-3. I believe that noise is getting into the BANDSEL and the microcontroller is detecting the voltage level as it moves outside the region set by the switches. The microcontroller then thinks that the momentary change in voltage was a band switch. C1 does not seem to be sufficient to keep out that noise.
It would be nice if a software low pass filter could be added to the code. Even a simple averaging filter could help minimize the noise pulses.
I like to do SKCC and yet this issue makes things difficult.
72, JP, K8AG