R7000P - Slow WiFi - Only getting 54Mbit on 2.4/5GHz

Hi, 

I´m having a really annoying issue with my R7000P router (FW V1.3.1.44_10.1.23). I´m only getting 54Mbit wireless link speed (PHY) on either the 2.4 or 5GHz. Regardless how close I am. This goes for both my LG G4 phone and for my HP Envy (2018) laptop. I know for sure both can handle much higher wireless speeds (I got 390Mbit on 5GHz at work today on the phone). The strange thing however is that my wifes Samsung Galaxy J5 is getting >300Mbit link speed on the 5GHz. 

This means I´m only getting maximum 30/30 Mbit in speed tests over WiFi. My Internet connection is at least 100/40 Mbit. 

Normally only 2 phones, 1 Chromecast (v.2) and a wireless speaker are connected to the router.

I have disabled QoS, Smart Connect and Traffic meter -> No difference

I have tried disable Beamforming, MU-MIMO and Airtime Fairness -> No difference

I have tried disable 5GHz and only running 2.4GHz -> No difference, still 54 Mbit only

I have disconnected all other wireless clients connected, only having my phone (LG G4) connected -> No difference, only 54mbit

I have restarted router, phone etc -> No difference

I think I´ve gone through most of the possible settings, I´m clueless and annoyed... Unless it´s the FW that is the problem?

Please help :)