Hi!
I found where the 404 page problem was – it was a windows server. There is no error on linux server.
However I think the solution with a slug formed based on the language of the site is not a good one. It would be nice to have a slug setting so that all event paths are identical. Otherwise we have several different urls on the site:
site.com/events/
site.com/мероприятия/список
site.com/event/event-name/