Annoying Windows bug that I still don't know how to make go away other than restarting

This isn't in "Report a Bug" because there's nothing Riot can do about it (it's a Windows bug; sometimes happens to me on other games). Just trying to find if other people have/had the same problem and/or a fix.

Sometimes (or in League's case, every loading screen and death screen), when I'm playing a game on borderless, I'll alt-tab out. Sometimes, after tabbing back in to the borderless application, the taskbar ceases to go under the application. It just stays on top. No matter what I do. Switch to fullscreen, switch back; hide the taskbar, unhide; move it to the top of the screen, move it back; still on top. The only fix I've found is restarting, a general annoyance, considering I'm using a HDD.

I guess this happens to me a lot because I constantly tab back and forth between the client and a browser while I'm waiting for the game to load.