Error 500 indicates that something went wrong on the server side and it should have logged something into your application logs. Check there and if you're unable to figure it out, post the relevant section of the log please.
Have you tried reindexing your Movie model?
You can within the console run
# BASH
rails c
# RAILS CONSOLE
Movie.reindex
or straight from Bash
rake searchkick:reindex CLASS=Movie
I think I'll do a followup episode on the FullCalendar with additional features, including the drag/drop support and recurring events.
Have a look at https://www.driftingruby.com/episodes/infinite-scrolling
It uses `will_paginate` but `kaminari` should be a fairly simple drop in with some minor changes.