When a sheet is protected, un-protected cells sre still protected. In Tools, Protect Document Protect sheet, Un-ticking "Protect sheet causes the app to crash
Please could you attach a minimal sample file where to reproduce the issue. (Remember this is a public site) Also you could try resetting the user profile. https://wiki.documentfoundation.org/UserProfile
Issue is withdrawn. I was thrown off guard by the double negative in the question. I need to pay closer attention to the question. I apologise for wasting your time.