Joseph, my 2350 was burping water back through the vent on the outside fill. I don't have the four way valve being discussed in the thread in our 2013 model. I checked the vent hose and it had a kink in it which allowed water to overflow from the tank to stop the air from venting. I replaced the hose with one a wee bit longer and that helped. Still at times, ours still burps.
My solution to the burping is simple. I cut a piece of vinyl 1/2 inch tubing to about a six inch length. When it starts burping, I put one end of the tubing to the exterior vent at the fill and simply blow hard into it, forcing any water in the vent hose back into the water tank. That immediately stops the burping by clearing that vent line from the fill all the way back to the tank.
I have had to do similar things on other rigs for the same problem over the years and I guess when going down the road with a mostly full tank, sloshing probably puts water in the vent hose. Overfilling can also cause the same problem with water in the vent line. I just bend the six inch "blow hose" a bit and it fits right behind the door to the fill pipe. Easy, cheap and just takes a little blow to clear and stop burping water back all over me.