In brief, I received a FMOD_STUDIO_EVENT_CALLBACK_STOPPED (from the callback) before the AUDIO_EVENT_CALLBACK_STARTED when I stop a “stopped event” and I invoke the play method later.
Thanks for the report. I have reproduced this behavior in my testbed. It seems the event callback gets triggered every time you call Studio::EventInstance::stop(), even if the event is already in the stopped state. This is a bug and will be fixed in the next patch release.