Modern caravans and motor Homes floors are made of a sandwich construction. The floor is constructed of two sheets of thin plywood bonded to a styrofoam core. If the bond breaks down, delamination takes place so your caravan floor will then feels spongy as you walk across it. Delamination can be cured injecting specially formulated epoxy resin, which takes up the void and rebounds the construction together.
Floor Delamination glue kits should only be used by a qualified caravan repairer.
This kind of repair is a permanent solution and the end result will be stronger than when the floor was originally manufactured.