Can't share calendar within the same group

[mokkin]

One of our new user (inside "VZL" group) can't share his calendar. The system reports the following errors. Nr. 19 was the default calendar, 21 an additional one.
The other user cannot see the the shared calendars.

Error OCP\Share Sharing 21 failed, because this item is already shared with detlef December 13, 2012, 11:01
Error OCP\Share Sharing 19 failed, because the user markus is the original sharer December 13, 2012, 10:56
Error OCP\Share Sharing 19 failed, because this item is already shared with detlef December 13, 2012, 10:56
Error OCP\Share Sharing 19 failed, because this item is already shared with VZL December 13, 2012, 10:56

OC 4.5.4, Firefox 17, Zentyal 3.0 x64

[DeepDiver1975]

please reopen this issue within the apps repo:
https://github.com/owncloud/apps/issues/new

THX