Interesting Troubleshooting Cases, Part 4 - The suddenly weaker Wi-Fi

Note: This article is part 4 of a 4-part troubleshooting series, with more in-depth information about a TEN talk at WLPC.
Part 1 - The RADIUS connection
Part 2 - Zoom issues
Part 3 - Breaking other Wi-Fi
Video recording from WLPC Prague

Incoming Ticket: The Wi-Fi is weaker now. Getting fewer bars, lower throughput on my Macbook Pro. Dropping out of Wi-Fi ofter.

Looking at the client device, I see a Macbook Pro 2018, and the signal and SNR are more than 10 dB less than usual. Not just a bit of fluctuation as expected between clients, but significantly weaker.

The other issue that stood out was that doing a lot of traffic right next to it dumped the SNR. Doing a speed test on an iPhone right next to it kicked the Macbook out of the network.

So I looked at more details, and noticed something odd:

It consistently did only 2 spatial stream connections to the 4SS AP, even if the signal and SNR were relatively high. Now we know, the Intel Macbook Pros were one of the few clients that had 3SS Wi-Fi, so this definitely was a clue and led me to the theory, that there has to be some sort of hardware problem.

So… I opened it up.

Macbook Pro open

Looks good, right?

Let’s zoom in a bit.

Macbook Pro zoomed in

Yep. That is one of the antenna connectors. It must have come loose somehow, causing low signal.

Reconnecting the cable fixed the issue - strong signals and high SNR again.

Remember: Even the “known good clients” can fail sometimes.