1. Be SURE you don't have a cracked heat exchanger. As I recall, you had a pro there who didn't suspect that, but who knows. You say you did some research on that and will be checking further. I'll leave that up to you to verify, be SAFE, don't take chances with the lives of you and yours.
2. As I recall, you said the furnace has two air pressure/air flow switches, they SHOULD trip if combustion air or exhaust are restricted, cutting of gas and the flame before "rollout" can occur. They can and do fail, the service manual (might find a downloadable version on the 'net) should have pressure ratings and testing procedures (typically using a digital manometer). In other words, perhaps there is an airflow restriction and the switch(es) aren't responding to it.
3. The burners are mixing tubes/venturis and with low gas pressure/flow it doesn't create airflow into and through the burner (along with the gas exiting the orifice) and gas will accumulate in the burner box 'til it lights off, likely burning at the back of the burner(s), (flame "rollout" by definition) and tripping the airbox overtemp sensor. Low gas pressure is certainly a possibility (again, can be checked with a manometer), required pressure range will be on the furnace rating decal.
4. The burners may need to be cleaned. Take a good look at them, best to remove for a good look and clean.
5. If your house is "tight" (little air infiltration) running bathroom fans and/or a range hood fan can cause negative pressure in the house and "flame rollout", but as your furnace is newer, and has a combustion air inlet and a sealed burner box, that shouldn't be the issue.
Some ideas. Again, BE SAFE, flammable gas and carbon monoxide are unforgiving!
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