My accelerometer's X axis (roll) is wrongly calibrated after OS update. I wonder why we don't have X axis calibration? There seems to be Y axis calibration tool integrated in VO.
Calibration apps don't work, VO doesn't care about external calibration apps.
Is there a way to calibrate it?

Not through VO. Although Android itself may have some calibration feature at the OS level.

If it does, it sure doesn't expose it to the user.

There is calibutil_yamaha. It's accessible through terminal with root, but it works only for samsung phones, placing and running the file didn't work for me,gave a bazzilion errors.