stereo at half volume?

I have a 95 m3 with:

alpine type R components up front

Eclipse CD8053

a 400w autotech amp 4 channel for the components

300w autotech for a no name 12 sub.

I used the existing factory amp wiring for the speakers up front and ran new power and ground to the amps.

everything worked great for almost a year and I eventually decided to make a harness so that I could take everything out for races.  A few months after I made the harness, I was driving and everything cut out after a sound.  Not a pop, more like when quickly disconnecting a sub when it is still playing.  anyways, I turned the deck off and wiggled it a bit and turned back on, everything was back to normal.  I did notice that if I was using the aux input, sound went completely out but if I was playing a cd, then the volume was cut in half.  Usually around 50-52 is the max I would listen (pretty loud) and after the issue, 50 barely noticeable with the car running.  After a few months of this happening failry often, I decided to take it all apart and start over.  First was troubleshooting: checked all voltage and connections, noticed a few looser than should be and re-attached everything.  Did not work and now the sound is stuck at "half power".  I tried running wire direct to speakers and still the same.  I have no idea what else it could be unless the deck is giving out... all the voltage was right at 12.5 (deck and amps). 

The strangest thing about all of this is that it would happen, I would turn the deck off, wait a few minutes and/or wiggle it, turn back on and it would work and now nothing seems to work......

Any help is greatly appreciated