RAX120 Slow 2.4GHz download speeds

I have Centurylink Gigabit connection and Wired and 5Ghz connection is performining as expected. WIred. I'm getting 900+ Mbps and 5Ghz i'm getting about 500-600 Mbps depending on where I am in the house, however i'm only receiving 20-40 Mbps when I'm connecetd to the 2.4 Ghz network. I've done a reboot and no help and even messed with the channels on 2.4Ghz and no help. Is this a problem with the router or firmware? I'm almosted tempted to return this as its quite expensive. 

Here is what i have set up:

Smart Connect: Off

Firmware: V1.0.0.84

QoS: disabled

Connection Type: PPPoE

SSID for 2.4GHz: Beast Mode 2.0

SSID for 5Ghz: Beast Mode 3.0