Apple Strudel... What went wrong?

[loveyouradvice]

Just made my second apple strudel last night ... filling is divine and best I've ever tasted.

But this time the filo didnt crisp up except for the single top layer.... Any ideas why not?

I used Jusrol Filo defrosted in fridge over night - plenty of butter in each layer, and sprinkle of demerera in a couple ... baked 40 mins at 180 fan oven...What do you think? Has this happened to you?