The issue is present for Revolution Flight Controller but may affect other FC aswell...
The initial accel/gyro calibration on freshly updated/erased board gives correct results. Subsequent accel/gyro calibrations on the already setup FC, i.e. with BoardLevelTrim.Roll/Pitch set to non-zero values and withaccel_bias / gyro_bias x,y,z also non-zero will produce results that are bad (shifted from zero).
To reproduce the issue:
Get a fresh Revo FC with initially performed all calibrations (especially Accel / Gyro / BoardLevel). Set manually in Object Browser:
Settings | AccelGyroSettings | gyro_bias.[X] = 1
Settings | AccelGyroSettings | gyro_bias.[Y] = 100
Settings | AccelGyroSettings | gyro_bias.[Z] = 1000
Perform Configuration | Attitude | Calibration | Gyro Bias Calibration | Start ....... Save
In the scopes Raw GyroState shows values for
X: -23.6 deg/s
Y: -6.6 deg/s
Z: -0.2 deg/s
These values are far from expected +-0.1 deg/s.
If the initial gyro_bias.x / y / z are "0" OR BoardLevelTrim.Roll / Pitch are "0" then calibration results are correct.
Same applies to Accelerometer calibration.