I don’t know how to replicate it either. The hundreds of broken links on Google and in my broken links plugin proved the upgrade crashed all the events. And there’s a few other things that have crashed (I don’t know exactly the day/time you upgraded GD, so I can’t tell the cause, which is what happens when multiple people make changes to a site without documenting their work) – but there are times my site won’t show images now (never happened before) and all my widget settings were deleted.
I’ve restored the theme settings, confirmed users are still able to submit events (both of which get removed during upgrades) and now will be troubleshooting why all my users are having such a difficult time submitting events. I’ve gotten more support questions and issues in the last month of GD than I did with 2 years on GT.