Baked Camembert disaster -help!

Yesterday for visitors I decided to do a baked Camembert in my new special dish. I have only ever been successful, achieving a lovely molten stretchy result when cooked in the box (oven and microwave). However, this time the cheese never melted beyond a lumpy blancmange texture. Why do you think this is? I didn't overdo it, was checking every few minutes, but it was a cheap 99p Lidl cheese. I had bought 2 of them so tried again today, without the lid, in the microwave with the same result. Do you think it was the dish, the cheese or me?