My broadband download speed has dropped from 500-550Mbps to 35-45Mbps over the past two days. The speed test looks like the speed is being throttled at a low rate. Any known issues causing this?

Every channel is pixelated and there are no reported service faults in my area. Have tried the troubleshooting tips which didn’t work and that redirected me to telephone support. Telephone support then took me through a few options and sent me a text...