User can't push button to send email via Gmail pack when a doc is in play mode

When a published doc is set to “Play” interaction, a user interacting with the doc in play mode can’t push a button that sends an email via the Gmail pack. Coda shows an error:

I verified that there is nothing wrong with the doc’s settings, and that the error comes from setting the interaction level to “Play.” If you change the sharing settings of the source doc to “Share” but don’t change anything else, the same user interacting with the published doc can send an email via the Gmail pack by pushing a button.

The error would seem to indicate that Coda needs the user’s gmail account, but even if the user is signed in, and even if the send-email button doesn’t depend on the user’s email address (e.g. it sends an email from the doc creator’s email address and to “example@gmail.com”), the same error message goes up.

Maybe this is a design choice, not a bug. My use case: I’m trying to create a Coda-made Docusign type doc. User reads an agreement, clicks some checkboxes to indicate that she understands and consents, and clicks a button to “sign” (write her name to a table) and immediately email the doc to our team and to herself. I want to let her click the button but don’t want to let her edit the doc.

Never mind—found a better solution! I can let people on my team edit the doc but lock it such that they can only push buttons, not edit text: