Sometimes when I go over a bump or take a turn hard, the volume drops by a fair amount (like in half - on all speakers). Note that the actual volume number on the deck isn't changing. The problem will eventually correct itself after another bump or hard stop/cornering, but not always. Very annoying. I've swapped amps and checked all wiring connections I can reach and nothing seems loose. Problem happens with seperate amps, so it's not the amp. Here is my setup:

Alpine IVA-W200 - Toslink out to:
Alpine PXA-H701
Audison LRx 6SR
a/d/s 336is seperates in the front
a/d/s 6.5" coax in back (not sure of model)
NVA-N872A Nav unit with XM traffic box

Could it maybe be the processor going bad?

 

Check/change your opticals. Its been known to happen from that...

 

i bet it's your battery, batteries are sensitive bumps and vibrations it makes them lose charge. once a battery gets old enough or worn down, speed bumps and turns can mess with their instant power output. yellowtops are pretty resistant to vibration, it's the way to go. I went through the same thing and the yt fixed it.