Time to find a new dealer to service the coach. Bad gas would not cause two cylinders to misfire it would cause 10 cylinders to misfire, randomly, along with difficulty starting, ruff idle, stalling and a list of other problems. And the shake down with the threat of the loss of warranty coverage, in it's last year for a 2016 model, is the candle on the cupcake.
Older gas is easy to fix by add new gas to the mix. If the tank is nearly full drain off enough to a 1/2 tank level on the gauge and refill the tank. Save the drained gas for use in the lawn mower, fire ant eradication program, civil unrest, topping off the tank on the daily driver or just back into the coach when it's a few gallon short of a full tank.
BTW, any problems with the generator? Same fuel source but being a carbureted engine the symptoms of bad gas would be much more apparent.