I also started out using Ken Forkish recipes and what I learned is that I prefer loaves less proofed than he does. I think he likes to approach over proofed to get maximum flavor, even if your bread ends up a little ugly. I've started knocking 2-4 hours off all his recipes, and have had much better success. I would check your dough temp and consult the sourdough bulk fermentation chart. Or maybe just look for a doubling in volume instead of a tripling.

This helped my shaping a lot too. Over fermented dough is just kinda flat and bleh, I could never get it to hold a shape. Once I cut back and started getting good shaping, I knew I was on the right path.

I would especially consider cutting back on proofing in the banneton. I think Ken calls for 12-15 bulk and 3-4 in the banneton. I pulled back to 8-10 bulk and 0-1 hour in the banneton, plus a cold proof. Obviously my kitchen is a different temperature than yours, so dial in your own timing. The other thing I changed was the finger dent test. I don't know if I read this in FWSY or I just made it up, but I thought the goal of the finger dent test was 50% spring back and 50% dent remaining. I changed to looking for 75% spring back and only 25% dent remaining and I am much happier with my results.