Annoying noise from oven vent

We noticed the same problem on a recent cross country trip. I tried just using the outside levers on the vent door, but it didn't work, ended up using the famous duct tape. That did it, for now. I might just go to the rag use, easier to take on and off. Looks like it is just a normal vent behind the microwave, not connected to the oven or stove in anyway.

Depends on the vent used. Some can be latched down, others are not meant to be latched. I have one of the latter on my range hood, it takes a certain set of wind and pressure conditions to make it rattle, when it happens I just live with it.

If your vent doesn't latch, and the rattle bothers you, you might try taping down the door. That's probably no more trouble than dealing with a vent door that has a latch.

I have no actual experience with an oven vent, the usual RV configuration is to vent all kitchen gases and heat through a filtered, powered vent in a range hood. Instructions for my range say to riun the vent hood whenever using the oven or range top, as both vent inside, as do residential gas ranges, If your oven is separately vented to the outside of the RV, advice may not apply.

Common problem - solutions differ by rig/owner. I just stuff a used wash cloth up into the outside vent cavity - ain't fancy but it works.

OPPS

I took the range hood out and put some eternabond on the thin sheet metal flapper. It's much quieter now.

It is pressure changes operating the draft baffle. Some have a latch pivot arm on the outside to secure the baffle.
Hard to see. In lower corners is latch.
Range hood vent

You will find that when you have a window open while moving down the road, that vent will rattle. When it's properly latched shut it is better but sometimes we still hear a little noise. The next time you hear it close all windows and vents and see if it stops.