Hi @LightStar, thanks for supporting this issue. Yes it happens with the original unmodified theme too:
Now I noticed that the text is shown too when resizing the window, as you can see in the gif above.
I'm on a clean installation of Windows 10 Fall Creators Update 1709, using the Flat Dark 10 substyle of your theme package, I did a clean reinstall of the Flat Dark theme package (after deleting the folder created in the public documents folder of Stardock) and I didnt touched/modified anything of the theme, any color, nothing of nothing.
I have not installed none related UXTheme patch that could alter the WindowBlinds normal behavior, and I don't have any other kind of personalization tool like WindowBlinds running on my O.S, well, just I have StartIsBack++ to change the start button, but that never before and now does not affect the style of explorer Windows, anyways I tried disabling StartIsBack++ to confirm it.
Testing more themes I noticed that this same problem happens in the default WindowBlinds themes (excluding the Aero Windows theme, of course), so probably it is a bug of WindowBlinds itself, maybe it does not support properly my Windows 10 version?... who knows...
I really think a moderator or someone with proper contact privileges than me should report this to Stardock dev. team, since this problem happens with other themes too, with all the themes... under Windows 10 Fall Creators Update 1709.
Here are my WindowBlinds10 settings if it helps for something: