This is a common problem where temperature changes are great.
The thin plastic cover is secured to the fiberglass deck. Depending on the stress due to the temperature changes, the headliner can crack.
My 282 had this issue. Once it works itself out, have the dealer repair. They use plastic and a heat gun of some sort, when done it looks ok, but if you know where to look you can tell it has been repaired.
My 300 will get checked this year before I splash, no problem yet, if so I'm sure GW/Dealer will address.
Bottom line, no biggie; easy repair and better than monkey fur...