Thank you for your post.
Fields formatted as Checkbox or Radio buttons operate slower on iOS devices than they do on Windows or Mac OS computers. Also, access to these formats tend to be more sensitive as the Checkbox or Radio button needs to be accessed precisely. Zooming in definitely provides more area for your fingers to access. Our Development and Testing departments are aware of this issue.
Some users have switched to buttons that executes a script to display the check mark (or remove), as this appears to work quicker with less sensitivity.
Let me know if you need additional clarification.