I know you said you replaced the self resetting furnace fuse with a "similar " one.
Maybe try a regular blue 15A fuse. The self resetting ones are notoriously unreliable.
The blades are thinner. You may have to give it a twist to make good contact.
Jim Vititow made a video about bad boards.
Intermittent furnace. Bad circuit board, heat gun troubleshooting. By Jim Vititow.
https://www.facebook.com/groups/2740...7964195593987/
His tech put a heat gun (hair dryer would work) on it to heat up the circuit board and it worked fine. They had 3 brand new boards do the same thing right out of the box.
It is also known Dometic had bad batch of sail switches. I know you said you changed it already. Some have had success bending the sail a little.
And or course, regulator pressure. I'm sure a gas tech would have the test equipment for that. Or switch the diverter valve to the other tank/regulator. Very unlikely both are bad.