When John Westlake was posting here, and developing what became the audiolab range, I seen to remember him explaining an issue with some capacitors that got specified, even from new. A lot of early MDACs had to get replacements, and a few were tweaked in the process I think.
What I don't understand is why this only affects your analogue input, as I thought the issue was around the DAC itself rather than the input. So perhaps it is something different.
@sq225917 Do you have any ideas? I can only really think you of you and Steven that night remember.