Calendar not showing events in monthly view (OC 9.1)

Steps to reproduce
1. Owncloud 9.1.4 with calendars migrated from OC 7.0
2. Calendar 1.4.1
3. Create Event in (shared) calendar and save. Isn't showing in monthly view.

Expected behaviour
The newly created event should be visible as soon as it was created in the owncloud-calendar.

Actual behaviour
After creation and clicking "safe", the event seems to be gone. When the Calendar-App is started in weekly or daily view the event can be created and is seen without any problems, only the monthly view seems to be problematic. Also, when the calendar-app is restarted in weekly or daily view after creating an event in monthly, the event is there.

Server configuration
Operating system: Ubuntu 16.04 LTS
Web server: Apache2
PHP version:
ownCloud version (see ownCloud admin page): 9.1.4
Updated from an older ownCloud or fresh install: 7.0.15
Special configuration (external storage, external authentication, reverse proxy, server-side-encryption): Authentication via external LDAP

ownCloud log (data/owncloud.log)

Integrity status for oC9+

No errors have been found.

Please always report such issues to the github bugtrackers. The correct for the calendar app would be

Thanks for the quick reply! Entered it there.