Very strange network issue - specific sites not loading

It ended up being caused by IPv6. I disabled it on my router and set it to IPv4 only and the problem is now gone.

All three of these sites appear to be HTTPS only, If you are starting which http:// addresses, these sites are informing your browser that they have move permanently to https with the 301 messages. This will be part of the 301 message. You may get additional redirects that add a path for the default page. The 301 redirects are likely a red herring.

Long delays like this are common if you have DNS conmectivity issues. However, I would expect that to occur on the first attempt.

All these sites are IPv6 capable. If it appears you have IPv6 capability, chrome will likely attempt to use IPv6 rather than iPv4 to connect. Negotiating HTTPS can involve several connections to different servers. If any of these are blocked or down it can cause delays.

It may help to use the Chome Developer Tools (CtrlShifti. Select the Network tab which will show you load times for page components. Hover over the first slow connection for details on timings.