Input.GetAxis returning nonsensical values for HID Sensor/GameController

Hi, I am running Unity 4.6 on Windows 7 64. I am using a device (tilt sensor) that Windows and Unity both detect as a joystick. Input.GetAxis("Vertical") returns reasonable values, but "Horizontal" has a neutral value of -.8, max positive (right) value of -.7, but a max negative (left) value of 1. In fact, when tilting left, it decreases from .8 to -.9 for a bit and then jumps to 1.

This does not make sense, clearly. Same behavior in Unity on Mac.

The Windows Game Controller Calibration tool behaves correctly, and I downloaded a josystick testing tool for Mac and the values it shows increase and decrease as expected. So it appears to be an issue with Unity.

I've seen this behavior documented in only a few other places, like here: http://forum.unity3d.com/threads/joystick-axis-output-wrong.234150/

But no solutions. Does anyone have any ideas on how to work around this? Will I need to create my own plugin to handle input from this device?