Bed adhesion is the most likely cause - give it a really good clean. You can also use a glue stick to help it stick better, but that’s often just a crutch that doesn’t address the root problem.

If you’re doing a holiday in the USA and renting a car via enterprise, Alamo or national book with Rentalcars.com, unless you’re flying with doing a Virgin package holiday, in Which case do it with them. They have the best rates in the market due to special agreements. If you want the best customer service experience for rental cars book with Virgin as they will put a lot of pressure on Alamo/national/enterprise who will bend over backwards for you.