I have been baking bread for over a year and occasionally have the problem that once taking 80% dough out of the proofing basket – it deflates. Many times the dough somehow keeps itself during pre-shaping and shaping, but it looks like it is losing its structure while sitting in the basket. I have this problem when using a relatively high percentage of starter in the dough and also with polish. But since it is not consistent, I cannot pin down the issue. Any advice will be appreciated.
I am about the last one to offer much help, but it sounds like over proofing to me. The basket helps the dough hold its structure so when you take it out, and it does not have that help, it collapses. That would also make sense when you are using a high percentage of starter, since it will proof quicker. Finally, are you sure that you are at 80% - that is , have you calculated the final dough by adding all the flour , including the flour in the starter, and then comparing that to all the water , including the water in the starter. If you have a high hydration starter, that will impact your final hydration percentage.