TP-Link TL-WR902AC v3 5Ghz Radio problems

Hi,
I have just flashed my TL-WR902AC with OpenWRT and from some reason the 5Ghz radio seems to be pretty problematic...

  1. When I use the radio as a client then it stops broadcasting the AP SSID, while the 2.4Ghz radio has no problem being a client and AP at the same time...
  2. When the client is on 2.4Ghz radio, and I only use the 5Ghz as AP it "rejects" any connection from my devices ("Connection was rejected", not a password thing).

I have read people had similar problems a few years ago but they all have been resolved by now... Any ideas?