GP-E2 Compass Problems
I've found the compass to be quite reliable. Occasionally when I notice it's off I recalibrate and all is fine. I understand it works like a traditional compass using magnetic fields to find magnetic north, so clearly ther are many situations, such as in a metal-framed vehicle, when it struggles to give an accurate reading.
As far as the screen going black during calibration, no, I've never had that problem.