Accelerometer Calibration returns success but does not calibrate

Hi all,

I’m running ArduPlane V3.5.2 and trying to calibrate the accelerometer with mavproxy. When I start the calibration, the plane returns

“Got MAVLink msg: COMMAND_ACK {command : 241, result : 0}

before displaying any of the “place the vehicle” messages. Occasionally, it will respond with “APM: Place vehicle level and press any key” immediately after “Calibrated” but it will not start the calibration.

Any idea what could be causing this?