Hey Javier,
Sorry to hear about these issues!
I cannot recreate theme on my own site, so I’m curious about what you mention here:
Something I noticed is that I can go back and see the event page and also see the progress bar doing the updates on the recurring events
1. ☝️ To help me more closely test your issues, can you share a screenshot of the “Time & Date” section of the event meta box for the event on which you have this 500 error? This “Time & Date” section should show ALL of your event’s recurrence rules. I will use the screenshot to try and replicate them exactly and see what I find.
2. Can you confirm what happens if you try to publish a non-recurring event? For testing purposes, make just one simple even that occurs on one day, and has no recurrence. Any issues when you “publish” this event?
Thanks!
George