some calendar entries are not beeing synced to the phone

Hello and good evening from Karlsruhe,

i´ve some problems with calendar entries not syncing from zimbra to my phone. Not all but only some and i actually dont´t know which and why.

I have a HTC Desire Z with Android 2.3.3 HTC Stock ROM, Zimbra Community Edition Zimbra 7.2.0_GA_2669 (Generierung 20120410002303) and ZeXtras 1.2.9.

Can you tell me how to fix calendar synchronisation?

KR JoeKar