Because its beta, or even alpha, its hard to say what is causing this. If you are experiencing it, its hopefully probable that others are as well. Have you considered using the Feedback Hub just in case? I wouldn't be too disturbed, as they are switching to Chromium, if they haven't already. I put my laptop on 201H1 (maybe I'm just a glutton for punishment at this point), but so far the build seems fairly stable that I am on. If its absolutely elusively annoying, you could revert back to the current version. I would try hard resetting the browser first.