I just saw your note.The responses get lost sometimes in the voluminous email text.
There is no CI-v connection to the PW-1. Just the one cable The Navigator is connected the the ACC on the 7800. I do no use rig control and HRD is used for logging only. No other changes have been made in the several years it has been working. The only change was downloading and using 2.4.
When going to FT4 and then back to FT8 then moving the dial from 070 to 074 it begins to oscillate by itself. Meaning the VFO's began going on and off the the other going on. After switching back to 2.3(not 2.3.1) it has stopped.
I hope this gives some ideas as to the area it might be affecting.