Try resetting the keyboard to its default settings. Expect that you will likely lose your custom dictionaries and word lists. I'd back those up before I reset anything.
Find SETTINGS, then LANGUAGE AND INPUT.
Tap SAMSUNG KEYBOARD (or whatever keyboard you have set as the default)
Find and tap RESET SETTINGS.
If your keyboard doesn't have a reset function, you can also reset the keyboard settings in the application manager.
Open SETTINGS, then find APPS (or APPLICATIONS)
Scroll down the list to find and tap on your keyboard (BlackBerry, SwiftKey, Gboard, etc).
Tap FORCE STOP, then STORAGE, then CLEAR DATA.