Coating the griddle bad

We tested the device extensively (we do Raclette not just for Christmas). The function as such is good. The pans are high quality coated and heat distribution is good. Negative is the griddle. The coating is bad, because the barbecue food bakes firmly. The coating peels off after 6 use, although cleaned with wooden spatula and dishwasher.
The stone must be cleaned always manually, but this is due to the system and does not make deductions.
Our unit is located after 2 years this way: All pans the unit with stone are in perfect condition. The grill plate can no longer be used. Total damage ..... Too bad!