Bakes well but falls flat after proving

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Hi there, I am pretty new to loaves of bread, I started my sourdough journey about 3 months ago. So far I've had a varying amount of success. lately, I started to use my pizza oven to bake the doughs with a combination of steamy towels and hot water tray. I manage to achieve a really good oven spring, but one of the problems is that after I lay it on the paddle it quickly goes flat and pools all over, which means that I can't really score it at all.

Now my question is does anyone know why it falls flat like that?

I have a few guesses but far from being knowledgable enough.

1. I do not use bannetons only glass/metal bowls lined with cheesecloth dusted with rice flour.

2. There's a gap between the top of the dough and the edge of the bowl so perhaps that fall is enough to kill it?

3. I used an 85% hydration dough, 75% bread flour, 15% Whole Wheat, and 10% rye flour.

In the end, I get a very big loaf, which rises very nicely but trapped because I can't really score it.

 

Thanks!

2 slap and folds spaced by 20 minutes after autolyse of 1.5 hours.

4.5 hours bulk rise with 6 folds in the first 2:15 hours. 

315 minutes folds then 3 30 minutes spaced folds.

Always kept at ~78F(oven light on).

Then proofs in the fridge for 12 hours at 4 degrees.

I am confused.  When you say you get good oven spring, that usually means that after final proof, you have loaded it on a peel, scored it , and during the time it was baking in the oven, it increased in volume.  If that is what is happening, I have trouble understanding why you say you can't score it.

If instead, you have mixed it, done a bulk ferment, shaped it, then done a final proof, and when you when to score it , it collapsed, that is a sign that you over proofed it.  While it is extremely difficult to determine when this stage occurs, you want to score it and load it in the oven when it has risen about 85% of the total amount it will rise, that way the last 15% or so will occur in the oven,  which we call oven spring. 

It is also possible that your hydration is very high, which can cause the bread to collapse when backing - I don't know what recipe you are following, but you might want to drop back to 75% hydration and see how that goes. 

"If instead, you have mixed it, done a bulk ferment, shaped it, then done a final proof, and when you when to score it, it collapsed, that is a sign that you over-proofed it."

It collapses on the peel, I score it as best I can.

When I bake it, it does spring up very well though, but the scoring does not open.

Isn't it suppose to be possible at any hydration level to keep it stable on the peel?

As you can see my scoring is there but it didn't open up.

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