Checkbox field crashes Appgyver iOS app but not preview on computer

I’m new at this so I am probably making a mistake.

Short version: I am reading the status of a checkbox. It works on my computer (in preview) but crashes the iOS Appgyver preview app on my phone.

Long version: I have a page with a button, a checkbox field, and a “checkboxStatus” page variable. I connected a “set page variable” node to the “onChange” event of the checkbox field and set the value of the checkboxStatus page variable to the value of the checkbox field component. So the page variable should be set to the value of the checkbox field whenever that value changes. I attached an “Alert” node to the button tapped event of the button. I bound the Alert message to the checkboxStatus page variable. So, on clicking the button, I would expect it to report the value of the checkboxStatus page variable (which should be the same as the status of the checkbox field).

On my computer, when I click the button, the message correctly reports the status of the checkbox (true or false). On my phone, the Appgyver preview app either reports nothing (when status is false/unchecked), or crashes (when status is true/checked).

I assume I have overlooked something. Any pointers are appreciated.