Possible bug with Text Scale function?

I’m running Scrivener 1.9 on a Windows 7 64 bit computer, and on a Windows 10 64 bit Surface Book laptop. It’s the same project on both devices, it’s stored in a Dropbox folder they both reference, and I’m very careful to make sure I’ve closed Scrivener on one machine and Dropbox has fully synced before opening the project on the other machine.

On both machines, I can use the Text Scale pop-up menu, or the menu or hotkey functions, to scale the text. However, if I hit F11 to go to full screen view, it doesn’t work. When I use either the menu or the hotkey to change the text scale, the ruler changes, but the size of the text does not. Then, when I go back to regular view in Scrivener, I can’t scale the text there either. When I attempt to, the ruler changes to reflect the new scale, but the text stays the same. If I shut down Scrivener and restart it, I can scale the text again in regular view, but once I hit F11 I lose that ability.

Any thoughts on how I can get this working again would be much appreciated.