Camera follow target issue

I have written a camera system where each camera is placed in a stationary position in the level, and can optionally pan or tilt (or both) to follow the player. This lets me have Resident Evil style cameras or allow them to pan around and cover both sides of a hallway or even tilt to watch the player going up and down stairs. The current camera is decided when the player passes through a trigger to set the active camera.

The problem is that tilt is coming out skewed. I have spent a lot of time already looking over everything and I cannot figure out where the problem might be. Hopefully someone can shed some light on the issue.

Here is the function in question (which is updated every $levelCameras::updateDelay from a master camera update function):

function Camera::updateTracking(%this)
{
    if(%this.getDatablock().className !$= "levelCamera")
        return;

    // calculate direction vector
    %dirVec = vectorSub(%this.trackObject.getPosition(), %this.getPosition());


    // pan ------------------
    %oldAngZ = getWord(%this.getTransform(), 5) * getWord(%this.getTransform(), 6);
    
    if(%this.canPan)
    {
        %rotAngZ = mAtan(getWord(%dirVec, 0), getWord(%dirVec, 1));
        
        %deltaZ = (%rotAngZ - %oldAngZ);
    
        // take the shortest pan
        if(%deltaZ > mDegToRad(180))
            %deltaZ -= mDegToRad(360);
        else if(%deltaZ < mDegToRad(-180))
            %deltaZ += mDegToRad(360);

        // if change required is too small, skip it
        if(mAbs(%deltaZ) >= $levelCameras::minFollowChange)
        {
            // smooth out the rotation - we don't want to 'snap' instantly to the new orientation
            %rotAngZ = %oldAngZ + (%deltaZ / $levelCameras::followSmoothing);
        }
        else
            %deltaZ = 0;
    }
    else
    {
        %rotAngZ = %oldAngZ;
    }


    // tilt -----------------
    %oldAngXY = getWord(%this.getTransform(), 3) * getWord(%this.getTransform(), 6);

    if(%this.canTilt)
    {
        %targetAngXY = mAtan(vectorLen(%dirVec), getWord(%dirVec, 2)) - ($PI / 2);
    
        %deltaXY = (%targetAngXY - %oldAngXY);

        // if change required is too small, skip it
        if(mAbs(%deltaXY) >= $levelCameras::minFollowChange)
        {
            %rotAngXY = %oldAngXY + (%deltaXY / $levelCameras::followSmoothing);
        }
        else
            %deltaXY = 0;
    }
    else
    {
        %rotAngXY = %oldAngXY;
    }


    echo("Orig Trans:" SPC %this.getTransform());


    // combine rotations ----
    %matZ  = matrixCreateFromEuler("0 0" SPC -%rotAngZ);
    %matXY = matrixCreateFromEuler(-%rotAngXY SPC "0 0"); 
    %finalRot = getWords(matrixMultiply(%matZ, %matXY), 3, 6);
    %this.setTransform(%this.getPosition() SPC %finalRot);

    echo("oldAngZ:"     SPC %oldAngZ);
    echo("oldAngXY:"    SPC %oldAngXY);
    echo("targetAngZ:"  SPC %targetAngZ);
    echo("targetAngXY:" SPC %targetAngXY);
    echo("RotAngZ:"     SPC %rotAngZ);
    echo("RotAngXY:"    SPC %rotAngXY);
    echo("DeltaZ:"      SPC %deltaZ);
    echo("DeltaXY:"     SPC %deltaXY);
    echo("FinalRot:"    SPC %finalRot);
    echo("New Trans:"   SPC %this.getTransform());
}