I finally was able to isolate another bug I stumbled first time upon a while ago. The symptom was that the permalinks of another plugin, JSON API, were occasionally rendered non-working and we couldn't use it to export data to our mobile application. After the second time I found the fix: it was to re-save the WordPress permalinks settings. Now the cause seems to be found as well. Here are the steps:
- Install JSON API and it serves your event data behind such URLs as example.com/api/controller/method/.
- Go to Events > Settings > Pages > Permalink Slugs and click Save Changes (All) without having changed anything.
- All JSON API URLs start serving only 404 Not Found error pages. No other URLs seem to be affected.
- Go to WP-Admin > Settings > Permalinks and click Save without having changed anything.
- JSON API URLs start working. No other URLs seem to be affected.
At the moment it's easy to accidentally disable the mobile app for every user by updating EM permalinks without remembering the extra step of re-saving WP permalinks after that. If this is verifiable for the Events Manager developers and can be fixed in a future update, that'd be great.