Hola Andres!
I’m sorry you are experiencing this issue too. Unfortunately, we haven’t had feedback from that user, so let me help you with the troubleshooting.
Could you please make sure all your Modern Tribe plugins (and WordPress core) are at their latest versions?
Once you verify you’re on the latest versions, please test to see if the issue is still happening for you. If it is, please enable WP_DEBUG and WP_DEBUG_LOG and share any PHP errors 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.
Then please share with us your system info by following this guide > https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Also, could you please see if there are any console errors by inspecting the pages where you have the issue? Here’s how you can achieve that > https://theeventscalendar.com/knowledgebase/using-google-chrome-developer-tools/
Thanks,
Victor