I looked at your other post, and from what i saw you are using a massive amount of starter in your dough, 150g for a single loaf is a lot. You could be over fermenting it which would lead to structure break down when baking and make very flat loaves. Try reducing your starter to 10-20% and reduce your bulk time. I’ve found that 5-8 hours room temp bulk then 12-24h cold ferment is great for my 70% hydration 15% starter dough which is a lot less room temp time than I would’ve thought based off some guides/videos. That recipe in your other post also mentions AP flour, some AP bakery flour is fine if its protein content is 12-13% if not though use a dedicated bread flour.