I'm thinking of buying a Trails West 4 horse trailer with an escape door but have heard that they are not well sealed. Is this true? Has anyone had any problems with Trails West horse trailer escape doors?

I haven't heard of any problems with the escape door seals. Have you looked at the door seals of the trailer you're considering? Check the water path. Pretend you're a drop of water. Start at the roof and work your way down to the ground. What keeps you from going into the trailer interior. The only rule you have is you can't go up. Any opening or crack is fair to follow.