Hello Philippe,
That is a bothersome issue. I have a couple of things for you.
First, you can always check to see if something you’re experiencing is a bug that is on our radar. We’ve got a list of bugs we’re working on over at https://theeventscalendar.com/bug-hunting/.
Second, somewhere in the list (#52 actually) it seems someone else reported a similar situation. If you check out their thread, there were some ideas presented and a possible workaround. Could you take a look at that and give it a try? https://theeventscalendar.com/support/forums/topic/events-all-marked-this-event-has-passed/
I’m hoping that does the trick for you until we get a stable fix released. Please let us know how you get on with it.
— Julie