Denser crumb towards centre of bread

Toast

Sorry if this is the wrong place to ask, but there's a problem I've been having lately with bread I bake. I'm using this schedule:

Friday 8-10pm: feed rye starter

Saturday 8am: mix leaven (20g rye starter, 100g water @30C, 100g flour)

8-12 hours later: mix dough: 150g leaven, 300g water @32C, 400g strong white flour, 25g wholemeal flour, 10g salt.

Apply three stretch and folds over first 2h 30; bulk for 3-3h30 total.

After bulk, shape and then prove for an hour before putting in the fridge overnight

Sunday morning: bake in a dutch oven at 250C for 15 minutes, then 230C for another 25-30 minutes (covered for the first 25 minutes).

This produces bread that tastes great but has that slightly gummy and moist touch to it. I also see that it has a much more open crumb  towards the bottom and outside of the loaf - which I confirmed in the end by slicing a boule in half horizontally and seeing a more open crumb on the outside. Below a re a couple of vertical photos showing a more open crumb away from the centre and a more dense one towards the middle:

 

 

What are the most likely causes of this? I always hear underproofing metnioned as the big culprit, but the dough seems to past the dent test before I put it in the fridge. Are there other ways to test proofing/is something else going on?

I had a similar problem and in researching came across mention in Kalanty's 'How to Bake More Bread', that dough which has been cooled needs to come back to 68-70F to shape/work and then return to 78-80F after shaping. Otherwise uneven proofing can occur resulting in gummy bread and/or tight crumb.

I took the temperature of my dough after it was out for 1 hour and  found the temperature was still below 60F! Apparently my fridge and kitchen is somewhat cool. 

For me what worked was to change my methods and I now do an overnight rise at room temp which works better for my schedule. Also I found I was handling the bread too much which forced air out of the dough. I now get a very open even lacy crumb that cooks through. 

I know some go from fridge right to baking but for me it has been problematic and tends toward gummy bread.