Trident TSM with random distortion on EVEN channels only???

[mkiijam]

Heading to the client's place this morning, but I'm not too familiar with the technical details of these consoles. Can anyone think of any reason why there may be distortion issues on just the even numbered input modules?

At first it seemed like the common pot issues, but why just the even channels?

 

[pvision]

Are the even-numbered channels all bused to the right output?Are you getting distortion at the channel inserts or the stereo bus, or numbered buses?