Corrupted idIndex and $loki value

[Miky88]

Issue #881 clearly shows the problem and it's still not fixed.
Basically the idIndex gets duplicate references and update throws a "Trying to update a document not in collection" error

[Losses]

I'm wondering why this happened, since many things of this library is buggy, I did a lot of research about the source code, if there're more detailed scenario about the issue, we may find the solution.

For my case, all the data with duplicated key are the same, they are simply inserted twice, what about your case?