Shokupan sides collapsing

I'm trying to make a large shokupan loaf (2.2kg) in a big ole Pullman tin. I'm having the issue where as it cools the sides pull inwards, collapsing slightly if you will.

I'm baking at 230c in a deck oven for about 45 mins and the internal temp is 95C

I've had this issue before scaling up loaves. Anyone got any ideas on how to avoid said issue?

Sorry I don't have the recipe to hand but can provide in the near future.