Upgraded today and instantly got a 500 error and the site became unresponsive.
Moved the-event-calendar out of the plugins folder and was able to get back in to the back-end. Grabbed a fresh copy of the updated plugin and tried to reactivate and got this:
Warning: require_once(/var/www/html/wp-content/plugins/the-events-calendar/public/template-tags/calendar.php): failed to open stream: No such file or directory in /var/www/html/wp-content/plugins/the-events-calendar/lib/the-events-calendar.class.php on line 164 Fatal error: require_once(): Failed opening required '/var/www/html/wp-content/plugins/the-events-calendar/public/template-tags/calendar.php' (include_path='.:/usr/share/pear:/usr/share/php') in /var/www/html/wp-content/plugins/the-events-calendar/lib/the-events-calendar.class.php on line 164
There is no "calendar.php" in the public/template-tags folder so this is a pretty glaring server-crashing bug.
Update RESOLVED: poked around and found that that file shouldn't even be called which reminded me I should clear my caches after the upgrade. Cleared my OPCode and nginx caches and was able to successfully re-activate the plugin.
I'll leave this here for anyone else having the same problem.