Hi. I confirmed this is happening at your /events link, but this isn’t part of our plugin.
I’m not sure which of your plugins or custom code you might have implemented on your site that would cause this.
Please follow our Testing for Conflicts Guide (basically switch to Twenty Sixteen theme and deactivate all plugins and custom code other than Modern Tribe plugins) and see if that helps narrow down the cause of this.
If that doesn’t work, please enable WP_DEBUG and WP_DEBUG_LOG and share any debug messages you see while changing tickets quantity, navigating your site’s home page, events page, single-event pages, and any other of your site’s pages relevant to this ticket.
Let us know what you find out.
Thanks.