Krita problem with 66,7% view - it's blured when animation plays on display

I’ve removed the ‘crash’ tag.

Your lineart is at a very low resolution so that the individual pixels are visible.
It’s not surprising that changing the zoom level causes noticeable changes.

For an animation, the important question is: When the frames are exported out to an intermediate .png sequence, in preparation for rendering into a video file, do the image sequence .png files look as they should?

You can test that easily.