Bechamel sauce in Thermomix

Bechamel sauce
(recipe from the book)
Melt 40 g butter in a bowl 3 min / 100 g / sq. 1 (in fact, it melts much earlier).
Add 40 g flour to butter and sauté for 3 min / 100 g / sq. one
Add: 500 g milk, 1/2 tsp. salt, 2 pinches of white pepper, 2 pinches of nutmeg and cook 6 min / 90 g / sq. 1

In general, my flour stuck around the knife and did not mix with the milk. Therefore, the sauce came out thin.
Tell me why this happened?

Bechamel sauce
(recipe from the book)
Melt 40 g butter in a bowl 3 min / 100 g / sq. 1 (in fact, it melts much earlier).
Add 40 g flour to butter and sauté 3 min / 100 g / sq. one
Add: 500 g milk, 1/2 tsp. salt, 2 pinches of white pepper, 2 pinches of nutmeg and cook 6 min / 90 g / sq. 1

In general, my flour stuck around the knife and did not mix with the milk. Therefore, the sauce came out thin.
Tell me why this happened?

In my book, which was given at the time of purchase, the recipe is as follows:
400 ml milk
50 g sl. oils
2-3 st. l. wheat flour
1/4 tsp pepper
1/2 tsp salt
a pinch of nutmeg
Install the butterfly, add all the ingredients and cook for 6 minutes / 80 g / sq. 2
If you add processed cheese, you get a delicious sauce for cauliflower.
If you add horseradish, you get a delicious sauce for meat.

I cooked with cheese. Everything turned out quickly, without problems and delicious. Try it.
For myself, I concluded that it was in this book that there were proven and more accurate recipes.