SteamVR tracker jitter 3x worse with Pro Base Stations

I'm creating a long-range marksmanship application. I mounted a Vive Tracker onto real rifle. The rifle is completely stable -- it's sitting on the table and I don't touch it.

This video shows the view through the scope. In the first half, I'm using all Pro hardware (HMD, tracker, and base stations). You can see that the jitter covers about 3 mils, which renders this application useless. In the second half of the video, I've swapped out the Pro base stations for the old base stations (and run a fresh room setup). You can see that the jitter covers about 1 mil, which isn't great, but it is acceptable.

I'm smoothing out the rotational data of the tracker; I average the rotations of the last 50 FixedUpdate cycles. Without this smoothing, neither tracker would be acceptable. However, this smoothing is constant between two samples.

I don't understand how the new hardware would be so much worse.

Has anyone else faced this problem? Anyone have a solution?