How to troubleshoot this?

I get an error message that is thrown at the console somewhere in three.min.js. It is quite cryptic and I am sure it is something I did wrong in my code.

But where should I start looking?

The message looks like this:
TypeError: b[c] is undefined[Meer info] three.min.js:319:98
> dispatchEvent
> set
> attach
> selectObject
> selectObject
> onMouseDown

If you know what it means, that too might help, but in a broader sense I am looking for some hints on how to troubleshoot errors like these…

It will be less cryptic if you use the un-minified version of three.js. The minified version three.min.js should only used for QS or production.