When I get random errors like this I find a couple browser tab refreshes does the trick. If it's still not helping, clear your cache - I've seen surprising things in WF that are fixed by clearing your cache. If still getting an error, see if happening in another browser. If you continue to get errors where you shouldn't be, submit a support ticket with what you've already done/checked/what browser you're using.
If this helped you, please mark correct to help others : )