LP Generator Starts then Stalls

I have an ONAN 5500 LP Generator. My 5th Wheel has 3 40 lb bottles. Two on a two-stage auto-changeover regulator, and one on it's own regulator.
The main lines from each regulator are connected via a T. The hose for the generator is connected to a T located at the output of the single-tank regulator. The gnerator has always worked fine. Recently Jayco did a recall to replace a potentially bad regualtor. They replace the auto-changeover regulator with a Camco model.

I recently went on a trip and tried to use the generator. The single tank is shut off, and the dual tanks are on. The generator starts, and then stalls in 3 seconds. Sounds fuel starved. I opened the single tank and the generator will start and run fine. I can run with only the single tank on, and the generator, 40,000 btu furnace and stove all run at the same time. If I turn on the dual tanks and shut off the single, the generator stalls and the furnace goes out. 30 seconds later the furnace re-ignites and runs okay. It seesms as though the new regulator can't supply the amount of LP that the generator demands. Has anyone experience this kind of problem? Any ideas of what I can check? (When they replaced the regulator they did a leak-down test but did not do a demand test).

Thanks!