I am having literally the exact same problem as you and have trying to get my issue escalated as well. I have swapped modems and still the problem persists. Let me know if you end up getting something fixed because this is legitimately affecting my wife and I's source of income right now.
I'm experiencing the exact same issue, it's getting ridiculous. It's been happening for a couple of months now. I have no idea why I pay for blast pro if this is continuing to occur.
Have you heard from a comcast representative yet?
This is what I get when I ping google.com directly connected to my cable modem. This is ridiculous.
20 packets transmitted, 20 packets received, 0.0% packet loss
round-trip min/avg/max/stddev = 14.783/100.547/417.696/113.310 ms a max of 417.696?!?!