Hi,
I found out now, what the problem really is. It’s a interface problem between polylang and wp-event-manager plugins. The rewrite_rules in wp_options are containing a lot of rules to rewrite event urls using /veranstaltung as a prefix for events (veranstaltung = event in german). Everything is fine I save some random english page. Doing so the prefix for the rewrites is changed to /event. Issuing a flush_rewrite_rules(), it’s set back to /veranstaltung again, because the default language is german.
The fix would be to add rewrite rules for all languages and translations for ‘event’, not just for the current active language.
I was looking at the code for some hours, but could not find the place where things are going wrong.
Any help is appreciated.
Magnus