Caldav Sync with Android

[winston6071]

Hello
I always used Caldav sync to our Zimbra Server, now in 8.0.5 version...
since some days it suddenly do not replicate entries done from the phone client side back to a shared calendar in zimbra, it immediately does it when i use the own calendar for this user. Nothing changed in the user rights inbetween.
I am pretty sure we used shared calendar entries for our clients already and suddenly shared calendar entries cannot be done anymore from the client mobile side. Is there something different or is there a bug causing this ?
the only thing we changed in the meantime was because someone asked that he cannot sync with his mac calendar... so we tried to figure out stuff and tried if the ical delegation setting inside the shared calendar mailbox changes anything ...
i already read a lot about this ical caldav troubles and shared calendar but it all concerned mac and not android till now .... i am worriing if there is a change somewhere, i will also ask the developer of the caldav app in the store
anyone has an idea or same issues ?
cheers joe