>>>
>>>With that correction the heading does seems to remain fairly constant regardless of beta and gamma values. But changes on the x axis still result in the skip :-{
>>>H
>>
>>

>Current code:

function compassHeading2(alpha, beta, gamma , absolute) {
>
>    var _x = beta ? beta * degtorad : 0; // beta value
>    var _y = gamma ? gamma * degtorad : 0; // gamma value
>    var _z = alpha ? alpha * degtorad : 0; // alpha value
>
>    var cX = Math.cos(_x);
>    var cY = Math.cos(_y);
>    var cZ = Math.cos(_z);
>    var sX = Math.sin(_x);
>    var sY = Math.sin(_y);
>    var sZ = Math.sin(_z);
>
>    // Calculate Vx and Vy components
>    var Vx = -cZ * sY - sZ * sX * cY;
>    var Vy = -sZ * sY + cZ * sX * cY;
>
>    // Calculate compass heading
>    //var compassHeading = Math.atan(Vx / Vy);
>    var compassHeading = Math.atan2(Vx ,Vy);
>
>    // Convert compass heading to use whole unit circle
/*
>    if (Vy < 0) {
>        compassHeading += Math.PI;
>    } else if (Vx < 0) {
>        compassHeading += 2 * Math.PI;
>    }
*/
>
>    return compassHeading * (180 / Math.PI); // Compass Heading (in degrees)
>}

With .atan2() you don't need the if (Vy < 0) { part - in fact, as it is, the correction may be done twice. Try to comment that part out (like I did here).