Some pictures would be useful. Depends on where the cracks are. My last van had aluminium roof and sides, abs rear panel and grp front panel. The owners club could advise on your specific caravan, although it’s not difficult to determine the materials by close examination. One forum member had cracks in his Fleetwood above the front windows. He repaired them with assistance from a specialist plastic technician. It was a big job that required stripping out all of the front end internals to access the defective panel area. Search threads posted by Gagakev.