I just updated the firmware to the latest version and am having problems with the 5GHz wifi connection. the problem is that it connects me perfectly, but it loses packets and it cuts the wifi.
Before updating I was perfect, without any problem.
As a wifi adapter for the connection I use the Archer t3u.

I have factory reset the router, changed the band, the channel ...
On the other hand, the 2.4GHz wifi works perfectly.

What I can do?

Thank you!