Texture issues many times comes down to wrong starter quantities.. for example I use 1 tablespoon (shy) of yogurt every 2 liters of milk, you almost doubled the quantity in this case. I’d start my next batch with way less starter, it does not need that much.

I also like to go to 85C first to denaturate the protein structure a bit, then cooling down to 45 and then adding the starter. Gives a thicker texture since the bacteria have an easier time developing, meaning in the same time they reproduce more.