As you can see in the image, his skills are maxed out thanks to his damage multiplier. Skills 2 and 3 are at level 0, even though they are maxed, and I've already chosen them. I tried to change to skill 3 because it shows skill 2 is selected, but then it says skill 3 is already selected.
Visual bug: Skills show level 0 when they are maxed, and incorrectly show which is selected.
It has happened every time I try to use him in the winter event; I haven't tried him out anywhere else.