Just in case anyone else got here via google, I can 100% reproduce this bug when there is an error in the initial parsing of main.js (and anything it calls directly on that parse).

This seems to cause the instance to re-parse the file, which will of course try to re-define the properties that you have already defined.

Why the change to createCreep and canCreateCreep?

Unless I missed something, I don't see any "reasons behind the change" parts?

This of course could be by design, but when a creep is spawning, it can also be recycled.

The spawn then continues to "spawn" nothing, as the creep was already recycled...