Post banneton troubleshooting
Hello, I'm baking sourdough every day in the cafe I work currently, our starter is pretty young 1mo, but fairly consistent, doubling and a bit more on a 12h overnigth cycle on the refrigerator. I'm using a standard 65% hydration full bread flour recipe that gets kneaded by machine half way and is finished with a few strech and folds. Bulk fermented with folds every 45 minutes for 4 hours then divided and shaped into oblong bannetons, left to cold ferment in the same refrigerator where starter feeds for 17 hours. Usually, not always it grows to about 1 cm from toppling over the banneton, when I flip it on the baking sheet the dough tends to fall to the sides. I do the regular cut and it goes into an oven with maybe too much steam (tray with boiling water). It grows significantly a lot sideways, I'm looking for tips to get more height out of my loaves.
If you bake daily then you'd want bread ready to bake in the morning. Since you're baking everyday your starter can be fed on a daily schedule and can almost always be active and ready to use within a few hours. You shouldn't need 17 hours which would make daily bakes more complicated. To start the ball rolling at the beginning of the week then an overnight final proof to be ready for the first day might be necessary for the first loaves but then after that one can have a bread ready within a few hours by using more starter. So you'll have breads coming off the "conveyor belt". Or you can have a schedule of breads for one day being made the previous day and final proofing overnight. But there really doesn't need to be a 17 hour lag for a daily bake. Perhaps speak to a bakery and get ideas for how they manage their daily bakes.
You don't show a slashed loaf, but the slash direction might be encouraging the sideways slumping. A deep slash along the long axis would do that. Several shorter slashes across the long axis instead would encourage upward growth.
It's also possible that the flour you use has something that promotes, or is a variety that has, extra extensibility. If so, changing to a different flour might reduce sideways slumping. If a flour contains, for example, some Sonoran flour, that tends to increase extensibility AFAICT. If your dough after the 4 hours of bulk fermentation is still fairly extensible or slack, this would suggest the flour has extra extensibility. It should be pretty elastic after the last S&F by that time. If that's not the case, some extra stretching just before plopping into the bannetons might help too.
My own loaves generally get two or three S&F sessions during bulk. More usually isn't needed. I do gentle stretches on the dough as I'm forming the preform, especially if the dough seems slacker than usual.