Looking at the pictures, one of the wires onthe XLR socket does not look right to me. As it was an EE that built these, I am surprised there is so much bare wire. It is not a safety issue, but it makes me wonder if this is a loose connection, which could cause a channel to drop out.
It will be worth checking out.
Funkified SL1200, Firebottle KIN, Neurochrome Modulus 686, Triangle Esprit Antal EZ, Pioneer PD-S703, Home built audio PC, RME ADI DAC 2 FS, DIY audio cables.