There is a bug where the router goes to 10 mbits mode after an reboot.
I had the exact same problem with firmware 2.271, and still have it now.
I could fixe the problem temporary by changing the wifi speed to 10 and then back to 300.
This is no longer possible on the newest firmware.
It’s really annoying. Router with internet from lan is fast 80-90mbits (I have 100mbits internet), when using it in repeater mode it dropes down to 3-9bits…