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If the main burner flame distorts at all you could have a cracked heat exchanger. Also check the combustion condensate drain piping and trap for blockages. Slime accumulation in the drain or trap can block condensate flow causing a shut down.
If the gasket was the primary cause the unit probably wouldn't fire up. What are you getting for a flash sequence on the control board when it locks out?
Does it restart on its own or do you have to cycle the power?
You should only have to cycle the power if you have a lockout and you're saying the board blinks normal operation, no lockout code. This makes me suspect the board. A bad connection is another possibility.
The shutdown occurs after the ignition sequence is finished. My service manual doesn't indicate this model has a Smart Valve. If that's what you have then the Smart Valve not the board would be suspect.
I have to step away for about an hour. If you have more question I'll respond when I return.
That's a Smart Valve