93 might be the freezer sensor?. Looks like the sensors are on the wall. There should be air vents in a channel that carries the air. The sensor would be in the airflow.
I would also check the door seal. If it's leaking a little bit of air it could cause your symptoms. Unlikely since it's new, but a simple test with a dollar bill against the seal when the door is closed - is it too easy to pull out.
It could also be what the tech said. Damper motor or fan...
The thermistor resistance may be off, meaning the control board is sensing a lower temperature than actual. Or a connector for that thermistor may be bad, adding resistance. One thing to try is pulling the connector for that thermistor on the control board and reseating it. Also pulling the...