Several contacts lost from Outlook.com

Hello, 

I use Office 365 and synchronize contacts between 3xDesktops (win 10), 1xAndroid (S10e) and Outlook.com.

One or two months ago I have noticed that some contacts have been lost. It already occured one or two years ago but within several days all have been back. Therefore I decided to wait. At this moment it is more than one month and contacts are not still back. As far as I know it is at least 15 contacts from more than 1000 contacts. So I presume it is more than those 15 which I have discovered.

Do you have some experience ? Do you know reason or may be solution ? Is it usual with Microsoft ?

Today I have been speking with Microsoft Support but they were not able to help me. 

Thanks for answers. 

Martin