What is wrong in these pictures ??

[#1]

Are there any similarities between the systems this is running on? Same ad-blocker, same anything really?

[#2]

There is only one similarity across the O/S & Browsers & both machines, is Avast's Online Security / Extension / Add - on That I can see (so - Far)
Which was also disabled during testing

[#3]

Don't know if it is a coincidence or not
However
After rebooting the router, the issue has disappeared