The common chime for backup assist, turn signal on to long, etc will periodically stop working and the only way I have found to get it to start again is to lift the leads on the battery.

This loss of chime sound is associated with the backup assist disable function in some way. If I either trailer my boat or have tailgate open such that the backup sensors (I assume) auto defeat themselves. Which I can understand. Trouble is that RANDOMLY the chime for everything else is disabled and it doesn't reset when not trailering or with tailgate shut.
Dealer is clueless but is more than happy to take my money and put vehicle on diagnostic machine although no one has heard of problem. Any ideas are welcomed.
ated