Howdy Robert!
Thanks for taking the time to report this. That is definitely not a known bug. We have been testing with 4.5 release candidates for weeks, and so far no one else updating has seen your issue that we’re aware of. 4.5 is running great alongside The Events Calendar in my installs as well. It’s likely something went wrong with the update, or perhaps there is a deeper issue here like another plugin that got updated at the same time?
Would you mind logging in so I can verify your support access? Or, if you don’t have/want a license (which includes a year of support) you should checkout the volunteer community on WordPress.org: The Events Calendar. It’s not the same level of support, but it’s free! We even check those forums once each week and help to the extent we can.
Cheers!
– Brook