Background: 1st Post, and I attempted to search for this problem and came up empty handed...

I own a 2003 Silverado SS. I installed a Kenwood DDX-514 headunit along with the Axxess GMOS-04 module a couple years back. Everything worked fine until now.

Problem: I'll be driving down the road, and the volume of the stereo will spike to full blast...I attempt to turn volume down on H/U, and it shows I am adjusting the volume but it does not adjust the volume. To get it to reset I have to pull over, shut off truck, and pull the fuse from under the hood. It will be fine for about 30 minutes then do it again. I double checked my wiring, bought a new Axxess box, and it still does it. I had the unit bench tested and they said it was fine, however they were not able to test it using the RCA ports...which the Axxess box utilizes for speaker output.
Anyone have any ideas?

Note: I did put the stock H/U back in the truck and it works as expected with no volume issues...

Any and all help is greatly appreciated. Thanks.