Sorry, I misunderstood your comment about the sound on power up otherwise I wouldn't have asked about the data cables.
The three audio amplifiers are attached to the heatsinks (left, right, and cabinet). The cabinet sound was out on my DE SW and I traced it back to the amp for that channel, replaced it, and all was good. Since you are hearing sound on power up, you'd think the amps would be okay. And if you look at the schematics, once you get to the amplifiers, everything is pretty straightforward from them to the speaker outputs. So I'd guess the problem is upstream somewhere since you are getting no or intermittent sound from all channels. If it was just one or two channels that were acting weird, I'd suspect the amps or something around them being flaky. I know I'm not helping much, I'm just thinking out loud to try and get some ideas.