OK, hmm. Well I couldn’t make much of it, so I googled it, and it took me to this older post here I wonder if you’ve seen: binding-errors-when-returning-an-array
There they mention the pointer to array was an issue, but just returning the Array was not, so perhaps that’s worth a look. But I don’t think that’s it, because why would that just pop up when you get at() in there.
So here’s my other thought: friend class. Maybe add a friend class MomentManager to the Moment declaration, and maybe that would expose whatever obscure generated private functions Godot is making for Moment to MomentManager.
That’s all I got for now, that’s a tricky one. GL.