Any Sprayable application if pounded on and not given proper time to dry between coats will bunch up and crack. Shops that do bed liners, undercoatings and rust proofing ofter dont let the vehicle sit between applications due to time for the job to double. Multiple small coats is key.
I washed the underside of my jeep, prepped it, scuffed it, degreased it, scuffed again, applied adhesion promoter, Waterbased Undercoating for a spray application, multiple coats over a 8 hour period, then coated with a clear chip guard. This process allowed the jeep to be lifted from a lift, seal the bottom of the jeep and allow another member on this board to wheel the shit out of the jeep in the hills and valleys of North Carolina without any issues.
Its all about applying the right item by the right person.