MongoDB EventSourcing OnStateChanged not called on every Version change

[arg-foo]

Sometimes, OnStateChanged is called not on contiguous Version updates.

Current
StateLogEvent - Version 1 submitted
StateLogEvent - Version 2 submitted

Sometimes, OnStateChanged is called with Version 2 without Version 1 prior.

Expected
StateLogEvent - Version 1 submitted
StateLogEvent - Version 2 submitted

At all times, OnStateChanged is called with Version 1 before Version 2 changes.