I just had a similar problem with a QU-PAC. It was intermittent and crackly just like a bad connection, but it was all outputs simultaneously. Only the AES3 was solid. After warming up a bit it would work. In troubleshooting I found a good whack would fix it. So I opened it up and sprayed/wiped all the ribbon and pin connectors with Deoxit. It’s now working fine, but of course the process of deracking and disassembling it could also have done that. We shall see how it lasts.
Obviously the bad connection had to be in the digital domain to affect all channels at once. The interesting thing to me was that a digital bad connection sounds a lot like an analog one.
Dale