Ode to Bourdin boule - shaping problem?

This was Take 2 of Tartine's Ode to Bourdin (white-wheat blend), and the first time that I tried using bolted flour (the previous loaves used bread flour in place of the bolted wheat flour). So this was actually 100% whole wheat, just with some if the bran sifted out and applied to the outside during proofing. 

The loaves looked fine coming out of the oven; perhaps a bit dark, one of them slid into the dutch oven crooked (but actually I might not be able to tell unless I knew), and the parchment paper stuck to the bottoms, which is annoying but easily fixed next time. However, when I cut into the first loaf I discovered a sizeable pocket right in the middle of the loaf. See below:

This is the loaf that went in crooked:

Whoops! Big 'ol pocket:

I was thinking that this was likely due to my not shaping it properly. Does that seem likely? Details are as follows:

I did an overnight autolyse, adding salt in the morning (probably should have added it at the beginning of the autolyse, but as with previous loaves I set my dough up and then went and read about the technique I was trying). Leaven passed the float test in 6 hours, so I mixed it in with the last 50 g of water and basically kneaded it into the autolyse. I did notice when I went to mix everything together that there was a little bit of liquid at the edges of the autolyse, making it look like the flour had lost some absorptive capacity - not sure if this was a product of me adding salt part way through autolyse, or something else. I was concerned about gluten breakdown, but to my non-expert eyes/hands the dough seemed just fine (stretched instead of tore).

I did a 3 hour bulk fermentation (room temp around 75 degrees F), shaped, bench rested for 30 min and did a final shaping. The loaves proofed in bran-dusted kitchen towel-lined glass bowls at room temp for 3 hours, then were baked in cast iron to 210 degrees F according to Robertson's directions. 

I'm still very much learning how to handle and shape dough, so I assume that I did something inappropriate during shaping to cause the pocket. (The second loaf remains unsliced as of yet, so no idea if it has a similar pocket.) Any ideas what that could be, and what I could do to avoid it in future? My husband reports that it tasted great with olive oil, but most of our bread goes to toast/sandwiches and that's more easily accomplished without giant holes. Also, it makes me wonder if my thermometer reading was accurate; would it be off if I accidentally stuck it through into the hole? I can't decide. I must need more coffee. 

Thanks!