Checkbox item doesn’t show on received message

I added a checkbox to opt-in to SMS messaging to our form by using the Selector field with one option, but it doesn’t show up in the email notification – there is just a colon at the beginning of the line where it should be and nothing else. I want it to work just like the checkbox consenting to retain data from the form after processing, which shows this:

: I consent to my data being retained by the site owner after this message has been processed. : checked

Also I noticed that when I save the settings for this field, the changes do show up on the website, but the selection of the checkbox selector is cleared in the QuickContact Form Settings (which means if I edit anything else in the form and forget to recheck “checkbox” that item disappears from the form). This seems like a bug, no? I have tried it several times, in different browsers, private windows, after clearing caches, etc., but it happens every time.

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