When you go back into the speaker set up menu, has the db volume setting to that speaker changed or not?
Does this happen with all inputs, HDMI and analog and the radio?
Have you switched the speakers, to see if the problem moves with the receiver or speaker?
If this is all inputs and the problem stays with the receiver and not the speaker, then it is service time for that receiver. You have already tried the reset which you should have done and still have the problem. Hopefully this unit is still under warranty.