x2 AsusZenWiFi XD4 Plus - WiFi Speeds dropping after minutes of setting up

[poolbeetse7en]

This issue has been driving me mad for the last few days. When setting up x2 XD4 plus nodes in a mesh or even AP, the initial speeds are excellent on both units at over 700Mb (I have 1Gb WAN), according to numerous speed tests. After an unspecified number of minutes, the speeds of both units drop significantly, and they struggle to get above 200Mb, even from a foot away. Both are using wired gigabit backhaul. I've tried both units as a mesh and separate access points, and the same issue occurs. I got so fed up with them that I ordered x2 Xiaomi Mesh AX3000 NE units to replace them with, but unfortunately the software on them is a mess, and for some odd reason, Guest network is disabled in AP mode, leaving only a single 2.4 and 5Ghz SSID which isn't enough for me, so they are no use for my purpose.

I went back to the XD4 unites again after boxing up the Xiaomi unites and once again, the exact same issue. Excellent initial speeds of 700Mb+, then both units just drop to <200Mb. Very frustrating! I realise this is probably plenty for most, but these units should definitely be capable of better speeds.

Setup:
Asus RT-AX56U with latest Merlin firmware - 3004.388.8_4
x2 ZenWiFi XD4 Plus with latest Asus firmware - 3.0.0.4.386_69095

Could this maybe be a firmware issue? Really appreciate any suggestions. Thank you!

 

[degrub]

It may just be a compatibility issue between the router and the two nodes. Ideally, you want all three devices from the same hardware (same model and version) and all running the same firmware. The latter may be the most important, but only experimenting will tell.

If you switch the two Zen units to AP mode and turn off the wifi on the router, then the above will be less important.

How much area are you trying to cover ? What you have should be good for more than most residences have square feet. You may be suffering from too much RF power, so set the two Zens and the router to minimum power and gradually raise after testing for coverage gaps. In fact, just start with the main router and generate a coverage power map. Then, add the Zen units where there is weak signal level and keep their power at just enough to have minimal overlap.