Jittering While Selecting with Lasso or Marquee in PS 21.2.1

How can I stop the jittering / strobing that happens now while using lasso or marquee? It's very distracting while trying to concentrate on pixels and it's giving me the heebie jeebies! Thanks.

Using Macbook Pro 16in 2019 / Catalina 10.15.7 / Photoshop 21.2.1