Certain brush sizes cause my screen to go wonky

Running latest version of Cloud P-Shop, Lightroom and LC - in all 3 programs, when I use the brush, my screen goes wonky - gets black from a point roughly at the bottom of the brush, duplicates screen image, flickering, etc.

Only happens with a brush of a certain size. In Photoshop, that size appears to be between 200 and 400 pixels. In Lightroom, it is size 6-12.

Smaller brushes, or larger, and the screen is fine.

Using an Asus Zenbook with touch screen, which I think may be part of the issue. windows 10.

Anyone else experience anything like this?

Thanks!