Missing data when calling HubConnection.On twice

Question

I'm calling Hubconnection.On method twice in my client code. Each method shuttles it to an observable subject on a threadpool. But I seemed to be missing some messages. Since all work is done asynchronously I'm confused as to why I'm losing some messages when I have a good internet connection. code example:

connection.On(methodname, _subject.onNext)
_subject.ObserveOn(Scheduler.Default).Select(_MapToNative);

In another code location doing the same thing

connection.On(methodname, _subject.onNext)
_subject.ObserveOn(Scheduler.Default).Select(_MapToNative);