Layout callback not working?

Somehow, "cb:" on buttons does not work for me. When i run the code example from the tutorial, i get

Uncaught Error: Function "a" not found!
 at line 1 col 1
a(this._l,b)
   ^
in function called from system

I tried 2v14 as well as the bleeding edge build. Funny thing is, about 5% of the time it works as expected, but usually not. I also get this error message when uploading via the Web IDE:

Error parsing JavaScript, but uploading anyway.
SyntaxError: Identifier 'a' has already been declared (1:1920)

This is the code:

var Layout = require("Layout");
var layout = new Layout( {
  type:"v", c: [
    {type:"txt", font:"6x8:2", label:"A Test", id:"label"},
    {type:"btn", font:"6x8:2", label:"One", cb: l=>setLabel("One") },
    {type:"btn", font:"6x8:2", label:"Two", cb: l=>setLabel("Two") }
  ]
});

function setLabel(x) {
  layout.label.label = x;
  layout.render();
}
g.clear();
layout.render();