iPhone 12 sudden drop in performance in 5 ghz Wifi

Hello everyone,

I have started to notice an issue with my iPhone 12 with the 5 ghz bands. I already had problems in the past, but i had particular network configurations that could explain that.

Now, i have 2 Xiaomi AX 3600 Wifi 6 routers, paired by cable and able to produce an unique 5 Ghz Mesh network. I have also 1 gb/s fiber internet at home with very low (10 ms) ping.

The iPhone is connected in Wifi 6 and most of the time the speed is great varying between 400 and 700 mb/s, with very low and consistent ping.

But sometimes, the speed suddenly drops to 250 - 300mpbs and most importantly, the ping is very inconsistent and have high spikes, varying between 10 and 150 ms. This is not a router issue neither an issue with my internet connection. I already reproduced the problem with another router at a relative's house also with fiber internet. Rebooting the router doesn't fix anything.

The only way to fix this is to reboot the iPhone, and everything is back to normal (for a few days at least). The drop in bandwith is not a deal breaker issue because wifi can be inconsistent, but the ping spikes are in my opinion, and apparently this is not related to my router or my network environement.

So, what can explain this ? Disabling Network assistance in privacy settings don't fix the issue. I have already private mac adress turned to off also. Is this a firmware bug ? A software bug ? Have anyone encountered the same problem ?

Thank you in advance for your answers !