I'm pretty sure that was on the bug list awhile back. I had thought it was fixed as I haven't seen it lately. But then I've mostly been messing on my insider machine

Yep, Donald's right. That's a known bug. That's been bothering me for a while now. I believe it's on their fix list. I'll double-check...

Thanks Donald and Richard for your input!

Werner, I checked back through the earlier reports, we're not the only one seeing this kind of display glitch. Other users reported incorrect highlighting and background colors in this earlier rendering-bug discussion, and I noted continuous forms not refreshing properly there too.

Microsoft is aware of related Access rendering issues. Some related bugs have had fixes, but I cannot confirm that those fixes cover exactly what your screenshot shows. So I would not assume you have done anything wrong with your form.