Sometimes when trying to add a statement, the text input field doesn't appear, there's just a loading spinner which never goes away. This was also reported at https://www.wikidata.org/wiki/Wikidata:Contact_the_development_team#Problems_with_Safari_using_present_in_work_.28P1441.29
I've never been able to reproduce it reliably, but it happens to me when I select a property and the text field for the value doesn't appear fast enough - I start typing and it goes into the property input field instead, which triggers another search (removing the text field for the value), then when I delete the text I typed and try to select the same property again, the text field won't load.
I have however come across another way to trigger it which is reproducible (for me in Chromium and Firefox, at least):
- Load https://test.wikidata.org/wiki/Q778
- Click the "add" link to add a new statement
- Type "country" into the property search
- Let it finish loading - it will display a text input field and move the focus into it
- Click "country calling code"
Instead of loading a text field as expected, it just displays a spinner which never goes away.