Deleted Calendar entries reappear once

Dear Experts-Exchange-Community,

sometimes Calendar Items reappear once after they are deleted. It happened 5 times the last five months. After they are deleted once more, they do not reappear.  This happened to four different Users, which are using different mobile devices (IPhones, Android Phones). The issue occurred while removing it in Oultook2016.

I dont know if the Problem occours with OWA and i was not able to recreate this.
The Exchange Calendar Repair Assistant is active. (Calendar Repair Mode)
The CRA Logs do not show entries for these Users.

I found one solution proposal:

Dont add a Meeting Location with [To:] instead use [Location:].
-> I can confirm that at least 2 times the error occourd the To field was used for this.

Key data:

Active Sync is used.

Windows Server 2016 1607 (Build 14393.1914)
Exchange 2016 v15.1 (15.01.1034.026)

Windows 10 Version 1709 (Build 16299.64)
Outlook 2016 Version 1710 (Build 8625.21.27)

I appreciate new ideas and solutions regarding this problem.
Oliver ZiegerAsked:
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Jackie ManIT ManagerCommented:
Were the deleted calendar from a shared calendar?
Oliver ZiegerAuthor Commented:
Hey Jackie,

yes they are shared indeed. Some only with LimitedDetails AccessRights, some also with Editior Rights.
What do you think?
Oliver ZiegerAuthor Commented:
The issue does not occur with current Updates.

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Oliver ZiegerAuthor Commented:
Problem does not exist with current Patches.
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