RAX40 upload speed outpacing download

I have recenlty set up my RAX40 with a new ISP (ATT fiber), I had to put my ATT router into a pseudo bridge mode. (same as in these instructions: https://www.f0il.com/how-to-arris-bgw210-700-modem-router-with-netgear-xr500-router/) 

After doing this, the RAX40 router is working and connected to the interent, there is no Double NAT situation or anything; it has a public IP address from ATT. So all should be good with WAN connection, but my LAN is having Issues. When I run a speed test through the Netgear genie on my phone I get great download/upload speed (600/300 mbps), but when I run a speed test on a device (PC, phone, or Xbox) I am getting speeds like: 50 down 250 up. This is happening whether connected through Ethernet (cat-8) or over wifi. 

This leads me to belive that there is some issue with my router settings, I am getting great speeds from the outside world but am expierencing a bottleneck for my local network. Any ideas on router settings I need to change? 

Note: firmware is up to date, all AX settings are enabled at either 600 or 1200 speed cap, QoS is currently disabled. I am happy to provide any other information that is needed. 

Thank you