Young Jedi needs help, you may be my only hope...

the crackle could be thin under layment… i.e. paneling instead of plywood… my holiday rambler had that issue, i had to use plywood pads to move around on the roof. anytime i had to get up there… i would defiantly not buy a rig with soft or crackling roof/panels/floor.
as the repairs may be more than what you paid for the unit….and to think of all the time you could be camping/fishing, instead of fixing a r.v.