"Error #1006: value is not a function" with mysterious cause

This is the line throwing the error:

trace((root as MovieClip), (root as MovieClip).manager, (root as MovieClip).manager.gotoAndFade)
(root as MovieClip).manager.gotoAndFade()

And this is the output:

[object MainTimeline] [object Manager] function Function() {}
TypeError: Error #1006: value is not a function.

How can that be possible? Or better yet, how do I fix this?

I’ve read something about “:void” return types causing type errors, but I already removed that. I’ve no clue on what to do to troubleshoot this error. I don’t even know what pieces of code to post.

Ah, and the rest of the code is full with “gotoAndFade” calls in the very same way it was called in this line.