Such a good question. Dimpling happens. And thankfully our bread tastest great even if the structure has gone a little wonky.
Dimpling for all my research and experience, and by the way, my recent 10 loaves all had dimpling and I know they were overproofed, slightly.
What can you do… you can try shortening the first rise to just double, even 1 1/2. Degas the dough as you divide and shape, and let it quite double in the final rise, just a bit over the pan. Leave a little rise for the oven and you can quite possibly give bid adieu to dimples. No guarantee, like I said, after hundreds of loaves I still get dimples, but I know it is because I let the bread get away from me and that the gluten structure has become tired.