SUMMARY

I have Korganizer synchronised with my Android 'phone using the Google Calendar app.

If I create an event in Korganizer with recurrences and then delete one event (in the middle of the series) from Google Calendar on my Android 'phone the whole series in deleted from Korganizer.

STEPS TO REPRODUCE
1. Synchronise Korganizer with a Google Calendar using the standard KDE feature.
2. Create a weekly repeating series with 11 entries using the Korganizer Add Event option and adding the repeating information.
3. Delete an arbitrary entry from the series using Google Calendar on an Android 'phone, using the delete this entry only option.

OBSERVED RESULT
All events in the series created in step 1. are removed from Korganizer.

EXPECTED RESULT
only the event deleted via the Google Calendar app should be deleted.

SOFTWARE/OS VERSIONS
Linux/KDE Plasma: openSuse 15.0 
(available in About System)
KDE Plasma Version: 5.12.6
KDE PIM: 17.12.3
KDE Frameworks Version: 5.45.0
Qt Version: 5.9.4

Android: 6.0.1