Modifying a gradient fill with a script

Have you used ScriptingListener.plugin to record the operation as AM code? 

// 2022, use it at your own risk;
changeAngleOfGradientLayer (30);
function changeAngleOfGradientLayer (theAngle) {
try {
var idset = stringIDToTypeID( "set" );
    var desc5 = new ActionDescriptor();
    var idnull = stringIDToTypeID( "null" );
        var ref1 = new ActionReference();
        ref1.putEnumerated(stringIDToTypeID( "contentLayer" ), stringIDToTypeID( "ordinal" ), stringIDToTypeID( "targetEnum" ));
    desc5.putReference( idnull, ref1 );
    var idto = stringIDToTypeID( "to" );
        var desc6 = new ActionDescriptor();
        var idgradientsInterpolationMethod = stringIDToTypeID( "gradientsInterpolationMethod" );
        var idgradientInterpolationMethodType = stringIDToTypeID( "gradientInterpolationMethodType" );
        var idperceptual = stringIDToTypeID( "perceptual" );
        desc6.putEnumerated( idgradientsInterpolationMethod, idgradientInterpolationMethodType, idperceptual );
        var idangle = stringIDToTypeID( "angle" );
        var idangleUnit = stringIDToTypeID( "angleUnit" );
        desc6.putUnitDouble( idangle, idangleUnit, theAngle );
        var idtype = stringIDToTypeID( "type" );
        var idgradientType = stringIDToTypeID( "gradientType" );
        var idlinear = stringIDToTypeID( "linear" );
        desc6.putEnumerated( idtype, idgradientType, idlinear );
        var idgradient = stringIDToTypeID( "gradient" );
    var idgradientLayer = stringIDToTypeID( "gradientLayer" );
    desc5.putObject( idto, idgradientLayer, desc6 );
executeAction( idset, desc5, DialogModes.NO );
} catch (e) {}
};