who owns/uses a LM_2?

It's most likely the controller or the gauge.
I've had an MTX-L that started doing this after some time. Worked for a couple of minutes then would crap out.
Tried rewiring it a number of times, no change. Changing O2-sensors altered the readings somewhat, but gauge still started showing error-codes after a while.
If it worked, the readings were all over the place too. Didn't even bother to look at it anymore one point.

Then one day I remembered I still had an MSD AFR-gauge (which is based on the same Innovate basics). Installed it and readings were back to normal and stable as it should be.