I can't say what was wrong with your first switch. Maybe it was broken. But clearly your video shows a typical Windows error which many users encounter every day. This OS tries to be "smart" for the average users and often spits out error messages b/c it misinterprets the real situation.

You can proof that the switch's web UI indeed is still alive after the connection to your Win PC is disrupted by connecting another PC/laptop to another port and load the web UI there while the first port is being tested. I bet that the web UI is still alive.

I can only tell you that every switch I got in my hand perfectly did run the cable test without any freeze or crash of the web UI or the switch, among those T1600G, TL-SG2008, TL-SG108 and some others There is definitely nothing wrong with the web UI. So I am convinced you misinterpret what you see in the video you made.