https://performance.cira.ca/ on top of being a speedtest site also checks your dnssec. Since it was mentioned that you are not using standard rogers dns, you should be very careful, as this puts you at the mercy of whoever is running them. That said, be careful with googles dns (8.8.8.8, 8.8.4.4) as they are a nice alternative, but I have personally had issues with them and encryption on websites in the past(exactly as you describe above).
Also, scan your system with malwarebytes as some malware will hijack your dns and may cause problems like you are describing.
