If the script exits and it's from the script code, it will do so with a popup message, otherwise it is definitely not the script which crashed
It is, that's why it is supported for several quests but not for all
As it says in the instructions, previously started quests are not supported for all 44, Waterfall Quest is not one of them
I'm aware of the bug and still working on a solution
Authed
The reason is most likely printed in the logger, it's usually when no quests are left to run
If you need any help just let me know what settings you used and I'll take a look at it