Procedure to reproduce:
- Start creating a new claim on an item.
- Use a URL property such as "official website"
- Add an invalid url such as "www.thebicyclingguitarist.net"
- Click save
- Receive "Malformed URL: www.thebicyclingguitarist.net" error
- Try to edit / fix the URL and realise you can't, because the text field is not editable anymore. You could just cancel and restart.
This also happens with the other data types.