The Corian guy is probably correct based on my experience fabricating Corian countertops. The 1/4" version used in RVs is subject to the movement of the RV, and if it's not installed perfectly flat, cracks will occur and will re-occur. If you get it repaired, make sure it's laid down over large blobs of silicone to allow for slight flexing of the base cabinet(s).
--2005 F350 Superduty Crewcab, 6.0, 4wd, short bed, 3.73 gears
--2016 Montana 3711FL, 40'
--SOLD 2014 Wildcat 327CK, 38'