[JRTJH]

The freeze plug sensor is inserted into the evaporator coils (inside the warm air return). If it is inserted too low in the coils, it will not prevent freeze-up in the coils. You might try moving the freeze sensor up an inch or so and monitor for performance. While the "factory setting" is usually OK for most installations, occasionally a bit of 'tweaking to get the best performance" is required on some rigs.

Here's a photo of the freeze sensor, you might check yours to be sure it's properly inserted (hasn't vibrated out of position) and is high enough in the coils to work properly.