In version 1.8.1 I saw this bug earlier.
When I add the "Wait" action to my FSM the send event wasn't appearing.
However, if I went to another FSM where I already had placed the wait action it showed up correctly. I could copy that action and paste it into my FSM and it worked correctly. I tried adding wait again to that same FSM and still got a wait action without a finishing event option.
Weird.
Attaching an image: