Thought the description of my problem was toilet bowl effect but after watching videos not sure. Phantom will not 'lock on' and hold position... Both altitude and over the ground. On the bench the Software Assistant shows all fine. Did recalibration on compass and IMU. Get 8-11 satellites, Course Lock and Home Lock both function ok. Altitude is erratic and Phantom drifts. The unit wobbles and never solid in position. I have another Phantom 2 Vision + that works perfectly. Have bound the erratic Phantom to another transmitter (basic version transmitter) still no joy. Would be happy to replace whatever might be bad but not sure if it is compass, IMU, GPS... Etc... Thanks!