Webflow form checkbox sometimes returns "true/false" and sometimes "on/off" (can't find a way to fix or replicate)

We have a classic Webflow form with a bunch of checkboxes where potential clients can select industries they’re interested in when sending a contact form. This form is connected to Zapier to send data elsewhere, and the setup worked fine when we tested and published the site. (The form was returning “true/false” on checkboxes that we set up easily in Zapier to filter our submissions).

But we noticed the form now also returns “on/off” on checkboxes instead of “true/false” in some cases, and we can’t find a way to replicate this behavior or find a fix. We noticed this in the “Site settings / Forms” where we a bunch of submissions got saved, but were only partially sent to Zapier due to not meeting our automation criteria.

We tried to double-check everything on the checkboxes, including the IDs and names (on the Webflow site), and fully reworked the Zapier automation as well to make sure it was hooked correctly. Also tried different browsers. Still works fine.

Did anyone face a similar issue with their default Webflow forms?

(Would share read-only, but the project is under NDA. I could potentially try to get some screenshots if necessary).

I’m having the exact same issue. It seems something around 1 in every 5 submissions has “on” instead of “true” value for the form’s checkbox. Interestingly, these submissions also have a field titled “0” that has the value of the submit button (e.g. “submit”). Otherwise this “0” column is empty.