DJI Phantom 2 Vision Altimeter Question

Hello,
While the Quad is sitting on the ground and I'm waiting for the satellites to lock onto the Quad, I see the altitude start creeping up. The altitude will start at about 8 feet and about the time the satellites lock in, the altitude is showing 25 feet. When I land the Quad about 20 minutes later, the altitude is at 47 feet. I'm using the DJI App for Android.
Has anyone seen this problem and know how to fix this?

Thanks
 

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