Years ago, heading westward across the Great Plains, ie, INTO a strong headwind, I noticed that my vent kept opening all by itself. I would close it, and next pit stop, it was open again. Evidently the vibration of traveling along with the high wind speed (wind speed plus speed of trailer) caused the vent to open. I used a bungy cord on the crank handle to keep it closed temporarily.
I then installed a MaxAir vent cover. It not only prevents rain entry when the vent is open, it also ended the vent opening itself when headed into a strong headwind.
I can see how the vacuum drawn on an RV with that vent open could interfere with the operation of the burner on a refer on propane.