XR500 horrible local wifi performance

I have an issue on my network I can't figure out. It started with having issues streaming local media content from an Emby server to wifi clients. Anything above 5mbps would have constant freezing. I thought it was an Emby issue, but it turns out it looks to be my router.

I tried to transfer a file from server to my PC and something weird is going on. At my PC I will get a wireless link of 780/650 on 5 band and 144/144 on 2 band. If I try transferring a file from server to PC, I stay around 500KB or less. I also see the same issue if I connect to the 2G band. If I transfer the file wired, I hit around 95MB, so it isn't a throughput issue of server or PC. And a speed test on the PC over wifi I get 50MB, so I would think my wifi has the throughput as well.

I also never experience issues with internet traffic. All devices on WiFi have no issues with streaming services, and I know they are going above 5mbps. I can achieve speed tests on those devices of over 300mbps.

It's been nothing but problems with this router model it seems. In the past, it was constant wifi crashing and only a reboot would get devices reconnected. I RMA'd that device and had this new one for over half a year now. I didn't have this issue with Emby in the past on this new router. I used to be able to stream direct so I was hitting up to 70mbps. 

Things I've tried:

rebooting all devices

updated XR500 to latest firmware 2.3.2.114

disabled all features of QoS

checked wireless channels I'm on and no one else is. Tried changing channels just to see.

Is there some setting in DumaOS I'm missing that would only throttle local network traffic when over wifi?