Cross-posting for reference:
@LinnPower The concerning part with the error message and screengrabs, is the missing “Property Editor UI Alias” (editorUiAlias). Which seems to suggest that some of the backoffice client-side files/assets are missing.
I’m wondering if this could be a similar issue you are/were experiencing with the localization texts? (Strange string added to ADD button). In that the upgraded client assets are either cached or missing from your server. 