This is not fixed by deleting com.apple.finder.plist -- found in your User Library/Preferences folder?
Since inputting Finder preferences again is relatively trivial, one usually just trashes the whole plist. Though if you are so inclined, you can open it in various editors and apps and make changes there.
Ignore Apples Reinstall answer, which they seem to be giving to everything these days - an unnecessarily huge step.
And yes, this is also the exact kind of issue where setting up a second user account, accessed by Fast User Switching, can tell you whether it's an account glitch, which are often not worth the time to track down. Though moving your stuff to second account is tiresome too.
Hope this helps, a bit confusing to answer below comments, which may have already answered.