As diagnosed in bug 1776862, sites using Quantcast's Choice/GVL-v2 cookie consent management library can completely break if it is blocked. Allowing at least two requests to not be blocked fixes this:

https://cmp.quantcast.com/tcfv2/42/cmp2ui-es.js
https://cmp.quantcast.com/GVL-v2/vendor-list-trimmed-v1.json

However, shimming this breakage doesn't seem tenable, as the precise copy and options used by a given site aren't clearly know to us. It might be worth reaching out to Disconnect to confirm whether this specific subdomain qualifies as a tracker, as they appear to consider the Quantcast TLD to be such.

An issue was filed for moving the Quantcast to Content category.

https://github.com/disconnectme/disconnect-tracking-protection/issues/295