Nighthawk R6700v3 poor wifi speeds

I currently have a fiber connection from at&t and use their modem/router with the wifi disabled as it is in the far back side of the house. I then have the nighthawk in access point mode in the middle of my house connected to the at&t box. When I use ethernet from the at&t box or the nighthawk the speeds are as expected 700-900 up and down. When using the nighthawk's wifi though the speeds are 20-40 up and down and that's even being right in front of it. As a sanity check I tried the at&t boxes wifi and I get an expected 150-200 even in the middle of the house by the nighthawk, on the other side of the house the speeds are 1-5 that's why I need the nighthawk as an access point. When I looked up the problem people kept saying it's a firmware but I downgraded, upgraded, factory reset, disabled everything people recommended and no change to wifi speeds. Since i'm already out of the return and customer service window am I just out of luck? Was thinking of getting a ubiquiti access point as netgear products have been really annoying and finicy in my experience. Also sucks that the nighthawk seems to be worth almost nothing reselling on ebay. If anyone needs anymore information please let me know.