I had the same problem The handle came off and when i tried to screw it back the scews would not bite because the wooden battern inside the wall had rotted.To repair it the inside of the caravan had to be stripped to replace the battern.If the grab handle is loose remove it and reseal with non setting sealant before fitting it.If you suspect water is entering above the handle from the roof try using crack finder available from most caravan shops which soaks into all the hair line cracks in the joints
Alan Slingsby, April 2006