Odd last troubleshooting thing I can think of is to try plugging it into one of your front panel usbs since they are usually using a separate usb controller. Otherwise you might just have a defective unit
Likely just a usb bandwidth limit you are hitting, try unplugging other devices that arent in use, I had this issue with my rift cv1
Edit*
Also plug your rift directly into a usb 3.0 port on your motherboard, hubs even powered ones can cause issues with high bandwidth devices
Back in my day we could only build to y=128, y'all got lucky