I don't have a 4K monitor to test with, but try a different font zoom size in your display settings, at least smaller. It looks like the position of the progress bar isn't being adjusted like it should. Maybe a different zoom would make it work.
Thanks for the idea. I think I've got a workaround for the problem using Windows 10 'scaling' option. It was set to 250% but adjusting it down to 200% has fixed the display issue.
Windows scaling in Windows 8.1/10 will handle a lot of the 4k differences, actually it does a great job of it. However, Adobe's software itself is poorly handling the 4k boom right now. I'm not sure what they're doing to fix it just yet, but I'm patiently waiting and working around it.
Right now I have 3 monitors running. I have two Acer 23" at 1920x1080 and a Dell 27" at 4k. The Acer's handle menus and such so I can read them while the 4k holds the picture. But with LR/Photoshop, that's hard to do because in order to properly develop in them, you need to have the main picture and menu all on the same screen. Why would I edit on a garbage 23" when I have a 27" 4k? Exactly.