Xfinity dropping DNS response packets

I use my own hardware. When using certain DNS providers, some specific responses are being dropped. These providers include ControlD and NextDNS. This has worked fine for months, and stopped working yesterday specifically.

I can tell the queries are getting out to these providers, just the inbound responses never make it back. However, using 'bigger' DNS providers like 8.8.8.8 work.

dig slack.com @76.76.2.0
;; communications error to 76.76.2.0#53: timed out