CSS animation help [CSS loader]

Question

I’m trying to make a css loader.
In the animation there’s something wrong.
I think it’s in the 100% or maybe I need to add 0% too.
The problem:
When you play the animation, after the 100% it kind of flicks (not smooth).
Before I added the border radius anim to it, it was just a square rotating around. And if you add a border to the parent of the element, you can see the element goes out of the border at the end.
https://code.sololearn.com/WCYVhkqvvt3D/?ref=app

Answer 1

It's running smoothly.