Haven't seen JOEL in thirty-five years but I remember finding the film quite disturbing, with some luridly gruesome shocks that rival those found in a certain demonic possession blockbuster released the following year.

A la publicity surrounding The Exorcist, there were reports of spooky on-set occurrences during the filming of Santeria rituals. I can't recall any of the particulars, only that there were some unnerving aspects -- perhaps a fatality -- that made the doings seem more than just a flack's fanciful concoction.