I second Dan’s comment. I noticed with my sms122 I would get a significant jump/drift triggering the solenoid when electricals adjacent to the probe line would turn on and off.

I’ve since ditched the probe in favor of constant CO2 during the day and O2 at night. My fish tolerate higher CO2 levels during the days if I run an air pump during the off hours. And, of course, there is less stuff to fuss with.