499 Errors reducing conversion numbers?

When I enable the “Support Rich Command Protocol” in the data tag (with the “use fetch” option selected as well), I get a JSON Parse error:
“Error processing response data: SyntaxError: Unexpected end of JSON input” stemming from line data-tag.js:123.

I’ve created a simple data tag with no extra event data or anything, straight page view with this option selected and the Fetch instead of XHR option selected and I get that error every time. Could you look into this for me?