Good evening Robert and welcome back!
Thank you for reaching out to us.
We are sorry to hear about the broken website after the upgrade! It was certainly unintended on our end.
I would love to help you with this topic.
Hans answer was spot on, you can get the core version on WordPress.org
That being said, if you are up for it (and for everybody’s benefit), I would be glad to try to fix what breaks when you update.
The best approach would be to use a copy of your current site on a test/staging environment (which is actually something that’s recommended for all types of WordPress upgrades).
Let me know if we could work together on this
Have a good week-end,
Geoff B.