Shower wall sealant not sticking

Purchased a gulfstream Capri
In the shower when we bought it we noticed the sealant on the seams of the paneling was coming off. The dealer re-sealed the seams and its somewhat holding. But it appears the caulking doesnt stick very well to the paneling material. Is there a specific type of caulking that may stick better? My only thought so far was to scuff the area at the seams with sandpaper to give the caulking something to grab.

Any ideas would be appreciated.