New created Exchange ActiveSync contacts get lost after a while

[da_paz]

It seems like there is something going wrong when syncing new created contacts with the eas.outlook.com server.
If I create a new contact with the native contacts app it is saved and showed within the app, but after a while it is lost. (definetly more than some minutes but can not say exactly)

Suprisingly manually syncing after creating a new contact neither leads to the same behaviour nor the contact is shown on/uploaded to outlook.com.
However, new created contacts on outlook.com get downloaded by the synchronization.

Unfortunately I can not find any setting to tweak or error messages.
Does somebody have an idea how to fix or further investigate this?

I am running Android 8.0.0
on a Xperia X Dual Sim (F5122)
Build 34.4.A.2.107

EDIT:

I am using an outlook.com/microsoft account and have added it as an account to the phone as decribed in Synchronising with Microsoft Exchange ActiveSync (support.sonymobile.com).

Only preinstalled android apps/settings are used. (so not gmail or other google apps)

[Strampke]

As far as I can read from your text it is a software problem either at Google or at Outlook settings.

I would act as follows:

- sync Google

- uninstall Outlook

- restart device

- install Outlook

- when creating the accounts it will ask you about sincing

[da_paz]

Sry seems like I have described my problem ambiguos.

Actually I am neither using a google account in this case nor the outlook app.

I am using an outlook.com/microsoft account and have added it as an account to the phone as decribed in Synchronising with Microsoft Exchange ActiveSync (support.sonymobile.com).

Only preinstalled android apps/settings are used. (so not gmail or other google apps)