Hi Ash,
I’ve had a very similar issue with an SQ console. Two or three faders would go to -infinity when changing layers. I sent the console in for repair and the tech said there was excessive amount of dirt and debris inside the console.
I paid somewhere between $300-500 USD for the repair. It hasn’t failed since. I don’t expose it to extreme environments, but I can’t deny that the SQ hasn’t been outside exposed to possible debris in the air…. I’m not sure what your working environment is like.