I know this is a bit dated but I just purchased a 384x288 4.5-18x and was having issues with the compass. It was locked on North and would then show ERR. I tried the calibration procedures multiple times with no luck. So I called ATN. He said that any news scope with new firmware is going to need to be calibrated. He sent me the instructions. This is the procedure directly from them. And it worked. It sounds crazy and I was skeptical. But it worked.
ATN Compass Calibration
Hello NAME, the following symptoms are directly related to the compass system when it needs calibration data:
*Compass stuck on North (N).
*Compass showing Strong Magnetic Field (SMF) when no electronics are around.
*Compass showing Error (ERR).
Please follow this procedure to perform a throughout compass calibration:
First, turn on the scope and wait until it boots up to the main screen where you can see the crosshairs, then:
Grab the scope with one hand and shake it hard in all possible ways for 1 full minute. Assume that you are trying to mix a bottle of water, but instead of shaking it back and forth, try to move the scope in all possible directions by moving both your wrist and arm. Don't be as gentle with the scope.
After doing that, the scope should say CAL for a few seconds and then the compass will show you the cardinal points if you move the scope around. In other words, it will be working properly.
If CAL doesn't go away, then turn off and on the scope and check again.
As a side note, this is something common on all digital devices and those issues mentioned above will be fixed by this procedure. If the issue persists, unfortunately we can either try to do the compass calibration once again, or we will have to create an RMA to bring the scope in for warranty service.
You could also give us a call and we can guide you better through the procedure.