On day 29-30, an abelisk falls with a message about wisps, at which point a fatal error occurs

Known issue, addressed in the hotfix, to be released

download version 0.7 and go to your world.  The event will happen and will not cause an error, but some things may disappear in your world. Then go back to version 0.8, and everything will work. The event will not end after restarting, only the arriving capsule will disappear