Too much gluten development?
There's one recipe I normally use, which is very simple, and around 71% hydration (150 starter, 300 water, 450 flour). I never have any problems, so I thought I'd move onto something new, which naturally leads to this post. I didn't follow a recipe, which might make this a little tricky, but hopefully my descriptions will be indicative.
I created a soaker, which I've not done before; it contained most of the flour (90%+) and left it for 24 hours. I added a stiff starter, and proceeded to knead what was a very soggy pile of dough. I've never worked with such hydration, so I thought I'd see what happened if I kept kneading - around 20 minutes. The end result was stringy pieces of dough when I took my hands away from it. Not particularly hopeful, but curious, I contined with 2 folds at 1 hour intervals, and a preshape/shape on the third. After a couple of hours on the counter, it went into the fridge for 20 hours. It proofed well.
Baking resulted in a small amount of bloom, and a pleasing distribution of air pockets. The actual bread, between the dough pockets is a little tacky/gummy - not ideal. This leads me to:
A long soak, with that much of the flour, plus 20 minutes hand kneading - is that the sort of point one would encounter over-development? Are the strong strands that appeared an indicator that this has happened?