If you click on BlizzMove in Twitch client and go to version and revert to v.1.9.3 then the problem will go away and from what I can see, everything still works ( I use it too).
Or here if you install manually: https://www.curseforge.com/wow/addons/blizzmove/files
I haven’t tried v.19.7 yet. Don’t want to log out of classic atm ::smile:
Edit: Notice the little red arrow to the right of the frame at the edge of the top of the window. Maybe the new version fixes it. It is a BlizzMove prob. though.