That is a step closer, though my tests didn’t reveal anything.
I put all 5 of out widgets into the “Sidebar Right” area, checked the home page and all looks good, no error messages. Then I went and deactivated / re-activated the PRO plugin. No change, no error messages.
Which widget is causing the issue? (Events list, Events countdown, Events Calendar, Events featured venue, This week events)
(Note, there is also a widget which is simply called “Calendar”, that is a built in widget of WordPress, nothing to do with us.)
When do you see the issue? When you drag the widget in the sidebar? On the backend or on the frontend? Can you send a screenshot as well?
Do you maybe have customizations / template overrides for the widget?
Andras