The AV2 can be rather sensitive to unstable voltage and also whatever is connected to it. Mini power cuts, of which I used to have a number every day could cause constant setting loss. I tended to ensure that cheap and nasties like TVs and the like were connected via an optical connection. Anything that floats at half mains voltage or connected to cable feeds is best isolated because it can scramble the AV2 settings and lock it up given half a chance, requiring a re-boot or re-set. Static shocks also tend to wipe settings too. I haven't tried lifting the signal to earth connection, but might be worth a try if the problem persists after taking all other precautions.
I think some work was done to try to lessen the AV2s sensitivity to this sort of thing so later post casework revision AV2s (or earlier units with revised motherboards and later Gen 6 processor board) may be better here, but I can't say for sure.
Thanks. I think I already knew most of what you say. Alas, I seem to need to reset/reprogram my AV2 every 2/12 or so. That's why I keep a printout of my settings. Don't even need to refer to the manual any more to do it, either! Really just nuisance value.
