PS Audio Ultralink (one) with terrible distortion

I have a PS Audio Ultralink first generation with a lot of distortion on both channels with also about 3V dc offset impossible to correct with the two offset pots that actually have no influence whatsoever). First I thought it might be a power supply problem because it's identical on both sides but all rails measure good and clean (although it has the exact same caps that leaked all over a Classé Audio Dac 1 I had to fully rebuild a few months ago they don't seem o be leaky here yet). I disconnected the outputs from the Ultra analog dac from the analogue output circuit but on the scope the distortion (visible on scope) looks still the same and the 3v are present right at the output of the dac. Is there still some hope that something before the UA chip is bad or am I being too optimistic ? Also if anyone has the schematic for this mdel that would be lovely (as it's not written on the cover I don't even know if it's the D20400 or D20400A version, is it possible to replace a basic version, with an "A" version ? )