Hi,
Sorry for the issues here. We introduce some coding from 4.0 and it is causing this issue.
We are working on a release, but downgrading The Events Calendar to 3.12.3 resolves this issue for now.
Filter Bar can stay at 3.12.1.
To downgrade use this link to download The Events Calendar 3.12.3:
https://downloads.wordpress.org/plugin/the-events-calendar.3.12.3.zip
You can download the older versions from your account here on theeventscalendar.com.
Once you have both zip files follow this guide to manual plugin changes:
Manual Updates
Let me know how that works out.
Thanks