My '04 Fleetwood does the same.
Although once the caulk has split it could let in water, water inside is not the cause of the splitting. The rig can sit for months and the caulk remains pristine; drive it a thousand miles or so, live in it a week, and the caulking is split again.
I'm thinking of adding a 1" strip of trim along the bottom edge, attached and sealed to the vertical wall but not the underside, letting the lower edge float.
Offline
