Garageband Track 1 & 2 signal doesn't register correctly

I sent back a Focusrite because I thought it was defective, and now have a Solid State Logic 12 doing the exact same thing, so it has to be Garageband or my mac. Once the SSL is plugged in, and all the mics hooked up, all mics gives an expected signal to the SSL. The signal shown by Garageband does not match them, and cuts out or doesn't show up, but just for channels 1 & 2 (3 & 4 work fine). I've swapped mic cables, and all work fine on 3/4. I initially thought the first two channels weren't showing up at all, and just recording muffled static, because they were bass and snare drum tracks. When I try to record sustained sounds, like a loud yell of frustration, the recorded signal comes in and goes out randomly like you're turning a radio dial slowly back and forth. It's super weird. It's almost like a compression or gate is randomly being applied, but these in are new projects with zero effects, and the settings match channels 3 & 4, which are working. I guess I could try out the free software that came with the SSL, but all my old projects are in Garageband. Any suggestions?