When registering a phone call and I want to add a description of the call, I click 'More fields' but nothing happens.

When registering a phone call and I want to add a description of the call, I click 'More fields' but nothing happens.

When registering a phone call and I want to add a description of the call ("meer velden" in Dutch), I click 'More fields' but nothing happens. I can not add a description. When I saved the call and then edit, I can add a description.