This is so baffling and does not make any sense. If it's not the OS (Sierra is the usual culprit), not a preference change, not the CAPS LOCK key, not a Wacom tablet. Computer restart does not help or resetting Ps prefs..........like this........
Start Photoshop and immediately hold down Ctrl+Alt+Shift (Windows) or Command+Option+Shift (Mac OS X). Then, click Yes to the message, "Delete the Adobe Photoshop Settings file?"
..........................the only other thing I can suggest at this point is for you to uninstall Ps and do a clean install.
The mystery continues... I finally gave up looking for the reason many of my tools looked like a small + sign. Then as fast as it came it went away. Was working on Ps last night and all of a sudden my tools went back to working normally. Go figure??? I have no idea why.