After a couple weeks of running with random MAC addresses I had mixed results. Usually the router would work for a day or two and then the problems would begin. Power cycling the devices (to get a fresh MAC address) seemed to reset the cycle. But this Thursday I seemed to run out of options. After three power cycles I was still experiencing masses of dropped packets (I’m not sure that’s a technically accurate description of the issue, but it will suffice). This made me think that the duplicate-MAC theory can’t be correct, because the odds of getting three duplicates in a row are astronomically low. Also, it was pointed out to me that Comcast may well have structured their network in such a way that duplicate MAC addresses aren’t actually a problem.
Thus I went back to cloning the MAC address off my working router. And lo and behold, that didn’t work either. So at last I removed the PCWRT router from the system and put my gigabit router in its place. That instantly resolved all issues. I’ve had an unbroken VPN connection ever since, streaming works, etc. I didn’t even have to reboot the cable modem.
From reading this forum it seems there are many users who are employing these routers without the kind of issues I encountered. I don’t know, perhaps they are just lucky. But my home setup is pretty plain-vanilla when it comes to devices, using a common cable modem that millions of other people are or soon will be using as DOCSIS 3.1 is rolled out across the USA. In any case, I can’t spend any more time on this, and will have to figure out another way to restrict devices on my home network.