Steps to reproduce
I have installed extensions 'WikibaseLexeme' and 'Form' in a third-party Wikibase instance. I have written down my steps at https://github.com/UB-Mannheim/RaiseWikibase#testing-all-datatypes.
The properties with datatypes lexeme, form and sense work without errors.
What happens instead
At an item's page with the properties corresponding to the datatypes 'lexeme', 'form' and 'sense' there are error messages: "Formatting error: Unknown data type '%'." In principle, the lexemes, senses and forms seem to work, the links are clickable, but the error messages appear anyway.