Ok, so I'm back again. I see you updated to 1.2.97.
I installed it and gave it a run, and the drift issues are still here. Using just Unity Chan as a test, by the time the performance was over, the headset had drifted about 45 degrees to the left and I was practically looking off of the stage. The headset would not correct for this drift.
As I've been saying, the manual calibration in 1.2.93 was the best solution to this. Just to re-test to ensure that I wasn't just imagining things, I reinstalled 1.2.93, ran it through the calibration, and loaded Unity Chan back up.
Performance was rock solid and straight ahead the entire time.
As I've said before, I get where you're going with the auto-calibration you added, but the manual calibration really should be back in as, at least for me, it practically solved the reason I didn't want to even touch the headset at all.
I want to also take advantage of the performance increases you've implemented, so again, I'd like to petition that you add the manual calibration back in.
Until then, for the sake of just being able to even use the headset, I'm stuck back on 1.2.93.