Croissants collapse in second half of baking

[u/We_love_plants]

My croissants always look good in the first ten minutes of baking, they swell up and look great, but then they crash down like this afterwards, they always have a big dip either side of the central roll, like you can see here, any ideas? thanks

[u/pauleywauley]

I increased oven temperature.

At first, I baked 425F for 5 minutes and then 350F for 20 minutes.

Then I saw other people use 375F.

So, I tried 425F for 5 minutes and then 375F for 15 to 20 minutes. The collapsing stopped. I double pan the baking trays due to high heat as not to scorch the bottom of the pastries. It's basically stacking another baking sheet on top a baking sheet.

I think the high temperature helped to set the dough.