sourceRectAtTime to adjust rectangles

[frosttho]

Hi,
first of all thanks a lot for this project. I'm sure I didn't use its full potential yet, but what I saw is great already.

I'm trying to build a graphic that contains text that is programmatically changed in a web project. Updating the text works perfectly. This text is supposed to be placed on top of a rectangle which should be as wide as the text. I tried sourceRectAtTime to achieve this, which worked great in AE but I couldn't get a working version through Bodymovin.
I looked into issue #300 and was happy to see that it is supposed to be working with text layers in svg as this is exactly my usecase but I couldn't find a mistake, yet.

I applied the following expression to the rectangle's size property (not the shape layer but the object inside it), referencing the text layer called "name":
obj = thisComp.layer("name");
x = obj.sourceRectAtTime().width + 25;
[x,value[1]]

My embed code in the html file looks like this:
json = {....}
animation = bodymovin.loadAnimation({
container: document.getElementById('anim'),
animationData: json,
renderer: 'svg',
loop: true,
autoplay: false,
name: "intro",
});
animation.play();

I uploaded the aep (Komp 3) and html files here for reference, if needed: https://www.dropbox.com/sh/4uok4dtrds7zioe/AAAPqxVLloDS4XKwc_wI-jsya?dl=0

I'd be happy to receive any hint that could lead to the resolution of this.
Thanks a lot!