Hyperlinks are automatically changed, leading to non existing page

Hello,

I have been trying for hours now to fix an error in my calendar. I have been using your plugin very happily for years, but now it is not working for me.
When you hover over the calendar on my website, it shows the basic info in a pop up, and then people can click on the hyperlink “More info and registration”, to go to the specific page where they can book the event or workshop. For all the last events and workshops I have put in (all of 2020 and one two day event in October this year), the links on the front end are different than the links I entered in the backend, leading to a “Oops this page does not exist” page.
There is an added element /workshops-and-events/ that I never put there but that is automatically being added and makes the link invalid. This has never happened to me before with this plugin. Can you please help me out as soon as possible because now almost nothing is working! Thank you.

The page I need help with: [log in to see the link]