Weird consistency , why didn’t it dissolve completely?

I made fior di latte, using this recipe: INGREDIENTS:

110g Sugar

60g Skimmed Milk Powder

550g milk (divided into 250g and 300g)

165g double/heavy cream (divided into 65g and 100g)

0.5g Xanthan

0.5g Locust Bean Gum

0.1g Kappa Carageenan

1g vanilla bean pulp

5g vanilla bean paste

TECHNIQUE

Thoroughly mix the sugar, xanthan, locust bean gum and carageenan together in a bowl with a whisk.

Pour 250g of milk and 65g of double cream into a pan

Add the sugar mixture to the pan and heat

Whisk to combine as the pan heats, and once it begins to simmer reduce the heat. It should nearly boil, and hold it there, whisking vigorously for 60 seconds

In a separate mixing bowl, or blender, combine the hot, thickened cream mixture with 60g of skimmed milk powder, the remaining 100g of cream and 300g of milk and the vanilla pulp and paste. Whisk/blend until completely combined.