I think you are missing the context in the following call

let​ frames = Array.prototype.slice.call(arguments);

I haven’t run the code yet but it looks fishy.

well what do I know? The second call with the null was the wrong one.

let​ frames = Array.prototype.slice.call(null, arguments);

One of these days I’ll learn JS.

Yeah, thanks Chet–this is a pretty embarrassing typo, and I’m glad people have mostly figured it out.