Again, when Photoshop suddenly starts to do weird things and it isn't due to accidentally having the Caps Lock key enabled, the first thing to do is always to kill the Photoshop preferences file. Here's what you need to do.
First, if you haven't saved your workspace, make sure you save and name your workspace so that you can get back to the same PS set-up after clearing the preferences file.
Next exit Photoshop. Wait a few seconds to fully exit the program.
Now launch Photoshop and immediately, and I mean immediately, before the splash screen loads hit the Ctrl ALT and Shift keys simultaneously (Cmd, Opt, Shift on Mac). This will load Photoshop and kill your preferences file. Now re-load your saved workspace. More often than not, this cures weird behavior in PS. The preferences file in all Adobe [products tends to be prone to corruption.