Early bikes had a white residue deposit in the fuel tank. Probably some wax leftover from manufacturing. Extreme cases can block the fuel filter. Wax floats, if you fill your fuel tank and see white flakes at the surface get the bike to the dealer for a cleanup and filter change under warranty.
Apparently this is affecting only known serial number and KTM is asking dealers with the affected bikes to remove the tank and clean it, with a picture send to KTM to prove they did it. No customer should experience this at this point.
Another example scarce on details.