WiFi Socket Error after setting up new user account

[EugW]

I have an old 2010 27" Core i7 iMac (with SSD installed) running OS X 10.13 High Sierra. It was running fine in my home office.

However, I set up a new Standard user account and moved it to my kid's room. Now for WiFi if I try to run Speedtest.net it usually errors out with a "Download Socket Error" if on WiFi:

Once I get that error, internet access just stops working completely.

Note that it's the same house, just a different part of the house. Both would be on Apple 802.11ac AirPort Extremes acting as access points, and the router is also an Apple 802.11ac AirPort Extreme.

My solution to the problem is to use Ethernet, as I don't get the error on Ethernet. But why is there is a problem on WiFi? It's only this one machine. Other Macs, iPhones, and iPads all work fine on WiFi, including from the same room as the iMac.

 

[Bigwaff]

You running the speed test from the Speedtest.net web site in a web browser?

 

[EugW]

You running the speed test from the Speedtest.net web site in a web browser?

Yes.

Basically if I reboot and surf the net over WiFi, it usually works fine, at least for the short times I've tried it. However, once I run the speed test and get the socket error, all surfing access stops working. This is true in both Safari and Chrome.

No such problems over Ethernet.

 

[Bigwaff]

Curious if the same thing happens with

Internet Speed Test

How fast is your download speed? In seconds, FAST.com's simple Internet speed test will estimate your ISP speed.

fast.com

 

[EugW]

Curious if the same thing happens with

Internet Speed Test

How fast is your download speed? In seconds, FAST.com's simple Internet speed test will estimate your ISP speed.

fast.com

It does not occur with Fast.com, but continues to occur with Speedtest.net regardless is if it's my Admin user account or my kid's Standard user account. Again, this happens only over WiFi. Ethernet continues to work fine.

My internet speed is roughly 600 Mbps down and 30 Mbps up on Ethernet. With WiFi it's roughly 150 Mbps down and 30 Mbps on this iMac in this room. There is an 802.11ac AirPort Extreme acting as an access point in the room below this one (connected to the AirPort Extreme router via Gigabit Ethernet), but this 2010 iMac is limited to 802.11n.

In the same room my iPhone 12 Pro Max gets about 240/30 Mbps over 802.11ac.