M1 MacBook Air issues with 5GHz WiFi

I recently set up a new router and noticed significant instability and performance issues when connecting to 5 GHz WiFi with M1 MacBook Airs. No difference in performance was observed among the other devices in our household - Windows laptops, Windows PC with PCIe Wifi Card, iPhones, iPads, Smart TVs, etc. We had a guest with an older Intel Mac that noticed no issues either.

So, we got to debugging.

• When using the 80MHz channel width for 5GHz WiFi, the speeds were unstable and the packet loss was abnormally high (20-30%).
• When splitting out a separate network for 2.4GHz WiFi, the M1 Macs had no issues.
• When setting the 5GHz WiFi to only use the 40MHz channel width, there were also no issues.

It seemed unreasonable to cap our network performance just for the M1 macs, especially when every other device had no issue. Furthermore, our previous router also used the 80MHz channel width for 5GHz WiFi, so what was the issue here?

I took a look at the Wireless Diagnostics Scan (available through option-clicking the WiFi symbol and opening Wireless Diagnostics, and then in the menu bar navigating to Window > Scan). I noticed that there were a few other networks using the same channel on the 80MHz width. After changing the default channel used for the 80MHz width, the performance issues were gone. Speed tests were returning the expected results and packet loss was less than 0.5%.

Hopefully this may help others experiencing WiFi issues with their M1 devices.

However, what's the root cause of this issue? Why is it that M1 devices suffer from performance issues in this scenario when every other device in the household was perfectly fine? One thing I did notice is that these M1 Macs are able to detect many more neighboring networks than the other devices in the household. Does this contribute to network interference, especially if there are other networks on the same channel in the area?