Android has a bug report Add support for external calendars via iCal / CalDav that prevents you from using a standard CalDAV application.
CalDAV-Sync corrects that bug:
CalDAV-Sync is a CalDAV client for Android to synchronize events. Due to its implementation as sync adapter it integrates seamlessly with the native calendar app and widgets.(Also check out CardDAV-Sync)
Important note for Jelly Bean users: To prevent the removal of your accounts on reboot install this app: https://play.google.com/store/apps/details?id=org.dmfs.jb.workaround.caldavsync
This app will create new calendars on your device (one for each calendar on your server account)
How exactly does it solve it?
Is it an alternative synchronisation? Or does it correct the bug?