Outlined icons have weird behaviours

Hello y’all!
I’ve been experiencing a weird issue with downloaded icons.
I’m using iconic’s free set, but some of them have weird joint vectors when I set the outline.

It looks as if 2 vectors were merged or close to each other, but when I look closer, I see no error? So I’m confused on how to fix it:

Has anyone had the same issue or knows how to fix this case?