Before I purchased RIFT S, I bought a USB 3.1 PCIE card (Startech). I had been using it up until yesterday with a 6' usb extension. Yesterday it quit working. Loss of tracking, stuttering, and blackouts. Eventually the light on the headset wouldn't come on even if i unplugged it and then re-plugged it.
Anyway, long story short, i went to device manager, and uninstalled the USB 3.1 Host controller. Then I went to Action (at the top) and scan for hardware changes. The card came back (apparently with new drivers? dated 6/18/19...) and now it works. I still got some stutter (or jitter), mind you. So i plugged directly into one of the USB 3.0 ports on the front of my PC (using a Texas Instruments USB 3.0 controller on the MOBO which Oculus software says is incompatible. Headset comes on - NO MORE JITTER/MICRO STUTTER. I don't know if this is a difference in USB port latency, port power output, or what, but the Rift S works beautifully now.
Just my experiences, your mileage may vary.