addCompToBatch issues

Hi!
I'm trying to add an After Effects project to the AME queue via scripting, but keep getting import errors.

The weirdest thing, is that I can add the same project manually without any problems!

My project has only one Comp on the root, and everything else inside a folder.

When I import it manually I get to choose the comp and it works great.

When I try to import the same project using ExtendScript I get this:

the code I'm testing:

var fend = app.getFrontend();
var ech = app.getEncoderHost();
var exp = app.getExporter();
//Input project file
var cmp = "/Users/valerialaura/Desktop/testingstuff.aep";
//AME preset exported to the desktop for later bundling
var pst = "/Users/valerialaura/Desktop/simple_preset.epr"; 
//Output files without extensions
var out = "/Users/valerialaura/Desktop/AME_rendering";
fend.addCompToBatch(cmp,pst,out);

Any ideas as to what could be happening here?
I also couldn't find documentation on AME scripting, so building over other forum answers and some poking around on ESTK.

Thanks!!

val.