Sourdough tin loaf bread

Hi, this is is my first post.

This is a sourdough bread, baked in a tin with lid(size 30 x 20 x 10 cm)

Is 2 kilogram of dough.

The recipe is a classic sourdough with 72% hiydratation, 15 % whole wheat , 2 % salt and 15% sourdough.

The process is kneading, bulk fermentation till 1,5x volumen, no folds during bulk fermentation, no preshape, just cutted, formed as a normal and retarded for 16/18 hours at 6 degrees in the tin with the lid.

Baked ad 250/240 degrees for about 80/90 minutes.

i make this recipe also for the house bread baked as a normal for loaf and no problem at all, but when It's baked in the tin with lid i get this strange hole at the top off the bread.

Sorry for my english, I Will appreciate if someone could help me to understand where is the error .

Thanks a lot!!!