Okay so I just traded in my Epiphone Thunderbird to help pay for a Dean Edge 5-string I've been saving up for. I jammed on it at the store after I purchased it and it sounded great. I took it with me to my band practice afterwards and jammed with the band for a good hour and we left to go out and hang out for about 2 hours. I came back and turned on my amp and no sound would come from the cab. I tried changing cords, playing with my guitarist's guitar through my halfstack(which it did play), changed the pick-up's 9-volt battery and still no sound. I thought I'd go home and plug it in to my practice amp to see if that would work and if not I'd take it to the music store the following day. I plugged it in my practice amp and it played. I jammed on it for an hour or so and noticed the amp's sound kept getting fuzzier and fuzzier, then it would cut out at times. I don't know what to do except take it back to the store and ask if they could help considering I just bought it, but I was wondering if any one here could help me as to find out what may be wrong with my bass? I run a Peavey tour 450 through a Behringer 4x10 ultrabass cab and my practice amp is a little 12 watt Kustom tube bass amp.
I've tried opening the back but the panel won't come off, its stuck tight and I don't want to damage my new bass. That was often the problem with my Thunderbird, I was constantly re-soldering the input jack wires back on because they evidently got fried off while playing. Could that be a problem my setup is causing?
If all the screws are out take a pencil and pry the back plate off. You shouldn't damage anything. If it hasnt been taken off before it just hasnt been budged for a while
Could be anything on those Deans. Take it back to the store.

EDIT: Try a couple of new 9vs. I've been fooled by dead out of the box ones before.
Fender Precision Bass
Fender Jazz Bass
1967 Fender Coronado Bass II
Warwick Star Bass
Squier Precision Bass TB