Weird, I just tested this in the new version of the plugin and it's working for me without any issues.
Hmm, the unspawnEvent function should handle erasing the event itself, it should only take that one script call to unspawn the event and remove the save data while removing all trace of that event from the map.
Does the event remain on the same tile after it's unspawned or does it move to -1, -1? It definitely sounds like something isn't working as intended.