The problem appears to be reappearing every few weeks. Usually, opting in and back out is sufficient to fix it again but it is incredibly aggravating having random requests fail to produce valid results due to the standards-breaking HTTP hijacking Mediacom is perpetrating upon its customers.
To date, I have not asked for or received any sort of compensation for the aggravation this issue has caused. I have opened a new thread in the Mediacom support boards asking for the problem to be fixed and for credit to be issued to my account for the fact that I have had to deal with this problem repeatedly.
The Mediacom board team has worked hard to try to solve the problem in the past and I am hopeful that they do so again this time. It is sad that such effective customer support people are being undercut by such incompetence on the network operations side.
Update: A Mediacom representative replied that they are unable to issue credit for this issue. I have replied requesting contact information for the entity that can issue such a credit. This should raise red flags with current and potential customers - Mediacom's initial response is that they cannot issue credit when the connection is not functioning properly due to Mediacom's own choices.