If it is a Dometic, depending on the version of lower air vent door you have on the outside of your trailer, they have a free kit that helps keep the flame on while driving. Call their tech support, tell them it blows out, & they will send you one. Didn't work for me because Escape
uses a different door - If you don't have any luck with Dometic, let me know; mine is available for the shipping. (Although you need to let me know soon - I'm heading out for 5 months next week!)
There are photos of the installation of the kit here
I solved the problem with mine by adding a furnace
filter on the inside of the lower door.