While adding items or voting, it is easy for people to accidentally click on (and focus) an existing item, which can cause confusion.
Possible fixes:
add a toggle to the page for enabling item focus, which defaults to off. This could be switched on per-device, allowing the main facilitator to interact while other users still cannot focus items
add a "start" button to the page, which changes the shared retro state. This might be more intuitive, but would risk other people affecting the retro once it has begun
use another gesture to focus items, such as a double-click (might be better to use double-click-to-edit though)
While adding items or voting, it is easy for people to accidentally click on (and focus) an existing item, which can cause confusion.
Possible fixes: