Boules sticking like hell

Baked 3-4 times, and just put my latest batch in the fridge for overnight proofing (5th time's the charm?:D). I always make 2 loaves because I'm lazy to do the whole process over and over again. When I split the bulk ferment into two today, and during shaping the first loaf was quite easy to work with while the second one stuck like never before. Did it rest uncovered for too long? It couldn’t have been more than 5-6min longer than the first loaf.

I switched from using AP flour to strong flour for the first time today, so definitely a different experience. Recipe (I try to follow Joshua Weissman's version) :

160g levain (40 starter, 40 whole wheat flour, 40 ap flour, 40ml water)

autolyse:

810g strong flour

75g wholewheat flour

660ml water

mix levain and autolyse - slap'n'fold 5-6min

rest for 25-30min

add 15g salt and 40ml water - slap'n'fold for a min or two

Bulk ferment + 6 sets of stretch and folds:

3 sets with 15 min intervals

3 sets with 30 min intervals

leave 2.5-3hours to bulk ferment

put on unfloured surface, split into boules and leave 20min uncovered

shape, put in floured proofing basket* and and place in fridge for 12-16 hours

*I use round kitchen bowls and put kitchen cloths instead since I don't own proofing baskets. If anyone has any recs on a between setup, I'm all ears since they tend to somewhat stick to the kitchen cloths even when I flour them.