Good evening Daniel and welcome to the Events Calendar Support forum!
Thank you for reaching out to us and for the system information.
We are sorry to hear about the mini-calendar widget giving you headaches!
I would love to help you with this topic.
Before we begin, I am noticing that you are 1 version behind on both the Events Calendar and the Events Calendar Pro version. After a backup, you might consider updating to the latest version (in case that helps).
By the looks of it, it seems that there might be some conflict at play.
Would you mind sharing an URL where this is happening ?
Other than that, our best bet is to go through our complete testing for conflicts procedure (preferably in a staging/dev environment or local install of your WordPress website) and let us know what you find out.
Basically the goal here is to revert back to a bare WordPress installation to see if the problem persists. It also allows us to pinpoint what the cause of the issue is.
My gut feeling is that this might be caused by one of the template overrides found in either the functions.php file of your theme or in it’s /tribe-events/ folder.
If you are up for it, I would love to take a look at that as well. Perhaps you could send me a copy via a link to a .zip file located in Dropbox or Google Drive ?
Best regards,
Geoff B.