Hey Qin,
I think v19 is the first run of the new re-factored event system (that's mod friendly). I'm pretty certain it isn't compatible with old saves. Currently testing only the Hale sisters quest. If there aren't egregious bugs we're gonna roll it out for all the existing official quests + mod guide. Then we'll enable event modding from the mod folder after it all looks stable.
Sorry for the event bugs, but I didn't see a way to re-do the whole event system cleanly while maintaining compatibility with prior versions/old-save event triggers.
There will be continual updates with the event system across this version (v19) as I fix up and adjust stuff. By v19d/e or v20 event system should be stable/good-to-mod.
I'll make a more official post for the event system after labor day weekend/monday.