Intermittent AC Off due to High Temp. Needle at Zero

Vehicle & History

• 2013 Chevy Cruze LT
• Replaced both the Water Outlet Valve and Thermostat 1-2 years ago (both melted at different times).
• After issue started I replaced the 2 Coolant Temperature Sensors. The radiator one with the tin pin sensor and the water outlet one with the gold pin sensor. Filled the system back up with anti-freeze and eventually it popped up again.
• There is a small ticking noise behind the engine. That’s been there for a while and I assume it is unrelated. According to this thread this sounds pretty normal.
• Only error codes from the reader are ones indicating temperature problems which I would expect since there seems to be a problem with the sensors.
• EDIT: Just noticed the plastic pin thing on the coolant reservoir is missing. I’m not really sure the purpose of this plastic pin. Is this a problem?

Issue Description

In the past 6 months the car’s temperature gauge started randomly dropping to zero and saying "AC Off due to high temp". Before dropping to zero the temperature gauge is never above half (so normal) and the coolant is where it should be. The temperature gauge sometimes works and sometimes doesn’t. It usually takes 10-30 minutes of driving for it to turn off, but it never seems hotter than normal under the hood. So it seems like a sensor problem, but I just replaced both of them and the thermostat was replaced not that long ago.

Next Steps?

All my searching seems to indicate these sensors or the thermostat, but I just changed the sensors and the thermostat isn’t that old. Any thoughts on what to try next? I’m getting tired of draining and filling coolant.