ZD1205 on 10.4.1.0 build 226
mixed WPA2/WPA3 wireless lan
My test devices:
- iPhone 11 Pro 14.2
- iPhone 12 Pro Max 14.3 Beta 2
- MBP 16" with both 10.15.7 an 11.1 Beta
- MacBook 12" running Mojave
- Old Huawei Android 6.0 phone capable of 5 GHz
Running dedicated iPerf server. Tested ~1 Gbps wired.
Most of the time iPhones typically giving me ~300-400 Mbps of iPerf bandwidth.
On any of my 3 home APs intermittently UL falls down to 70 Mbps, DL to 30-40 Mbps.
No interference, tested with Sidekick.
My temporary solution is to disable WiFi on device. Wait 20-30 s and reconnect.
In most cases it is working.
"This is a client device problem" - you may say...
Several clients with excellent connection (866 Mbps PHY on both ZD GUI and on device) experiencing it simultaneously. While connected to the same AP. So it is definitely an AP/ZD problem.
"Several clients with excellent connection (866 Mbps PHY on both ZD GUI and on device) experiencing it simultaneously. While connected to the same AP."
Could you check if everything is fine on wired network side? Like congestion on switch or high broadcast/multicast from wired to wireless or vice-versa?
You already did a lot of troubleshooting so I think opening case with these observation will be more helpful to debug the issue.