Kenmore gas dryer not heating (intermittently)

OK, hoping someone here can help. My dryer starts up, drum spins, but the flame does not start. Every once in a while, it will, but most cycles it does not. The ignitor glows for several seconds, then turns back off without lighting the flame.

What I've done so far:

• Checked the exhaust system (inside the dryer and in the house) for blockage (inside duct was fairly dirty, cleaned it but no dice)
• Tested the fuse near the exhaust motor for continuity
• Tested 3 thermostats for continuity (one by the fuse, two on the heat intake duct)
• Tested the flame sensor for continuity
• Tested the ignitor for continuity
• Tested the solenoids for resistance, one showed approx. 1,000ohms, the other ~1300.
• Checked the orifice for blockage, it was clean
• Gas supply is fine, as it sometimes does fire up

All items I've checked so far have been OK according to everything I can find in various forums. I don't really have the money for a new dryer atm, hoping there is something I'm missing.

Thanks