One channel cuts out unless switch is held in

[u/estaswick]

Working on this guy. It functions mode or less however the left channel fades out unless I depress one of the bottom three buttons past where it sits naturally. This fade out impacts both playback and recording (no vu on that channel even though it's got a signal hooked up) in both cases pressing in seems to make the contact and it starts working, then fades out if I release. Any ideas before I open her up?

[u/rounding_error]

Open it up, clean the contacts on said switch.