Could you please try resetting the preferences of Photoshop and let us know if it helps?
To restore preferences quickly using a keyboard shortcut: Press and hold Alt+Control+Shift (Windows) or Option+Command+Shift (Mac OS) as you start Photoshop. You are prompted to delete the current settings. The new preferences files are created the next time you start Photoshop
Sorry to take so long to respond. Resetting the settings didn't resolve it. I think at this point it's actually gotten worse, because restarting Photoshop doesn't usually fix it now.
I've also reinstalled Photoshop and updated it at least once since I first noticed this issue. The problem is it's intermittent so I occasionally think I've fixed it but it always comes back.
Certain actions DO refresh the window. For example, most tools like the brush will update the window. But selection tools (marquee, lasso) don't, and actions like Edit > Fill don't.
Any other suggestions? Would uploading a video of the behavior help?
I have "Use Graphics Processor" unchecked in Preferences > Performance.
It also just dawned on me that I'm using a new computer since I first posted this. I'm now on an iMac (Retina 5K, 27-inch, 2017) with a Radeon Pro 580 8192 MB. So I guess it's not hardware-related.
Is there a list anywhere of software that conflicts with Photoshop? At one point I thought Fantastical 2 was the culprit but then the problem returned without it. It's tough to troubleshoot such an intermittent problem.
There's a couple of threads here about the issue might be worth reading through to see if any of the suggestions work for you
Have you tried updating to CC2018
Thanks. I am using 19.1.3.
Reading through that thread it looks like RightFont is likely the culprit. I haven't paid to upgrade to the latest version of that but I will and see if that does the trick.
Thanks again for your help.
You're welcome hope you get it sorted