I have raised aspects of what I recount here past but I am not sure it has been appreciated, and it certainly hasn’t been fixed. However, I have not experienced the large scale deletion that has occurred over the last days.

I am not sure of the interfaces and programmes running on Android, Outllook.com and Apple platforms, but they certainly aren’t playing nicely together when syncing contacts. It has been a source of annoyance until very recently when actual damage has been done.

My personal experience relates to the Android Outlook app (and therefore Google’s Contacts app as this is where the Outlook app manages contacts), but there are issues on Apple/Outlook.com platforms too as my wife experiences the duplication issue on her iPhone. WhatsApp might also be part of the issue.

I feel obliged to say that none of these issues present on my Windows Phone – the sync routine is rock-solid.

I use Outlook.com and Outlook 365 on two Windows 10 computers. I use the Outloop app on my Android phone.

Issues with contact management and syncing:
Some contact entries duplicate on the phone (each contact appears twice) – they don’t duplicate on Outlook.com or on the computers.
When choosing a contact on the phone to edit, it is reported that the contact has been linked (with both linked contacts reported to come from Outlook).
Google (I think it is Google) takes it upon itself to combine (link) some contacts, but it often does this badly, e.g. I have a London contact and a Brussels contact for my wife. They share the same e-mail address, but the numbers are different and I use the suffix field in Outlook to differentiate the contact, but Google thinks it is very clever. Thankfully the contacts have remained distinct in Outlook and Outlook.com (on the web), but on the phone these often get “linked” – unlinking them manually can sometimes solve the problem
Duplication doesn’t occur immediately on the phone from the initial sync, but recently gathered pace until it appeared that all the contacts had been duplicated.
Last syncing issue worth mentioning is contacts with “complicated” surnames, e.g. multiple word surnames like “du Plessis” or “Janse van Rensburg” (or in a few cases if something appears in the suffix field) – Google (again I think this is Google being clever) decides to rearrange the name into the middle name field. This properly messes things up.

Resetting the account does not address the problem nor does deleting the app and reinstalling it, clearing caches and all the other usual stuff suggested by Support.

Last week I decided to disable the syncing (in the settings of the Outlook app). This obviously removed all the Outlook contacts from the phone. Enabling the sync again in the Outlook app appeared to bring all the contacts back from Outlook.com unduplicated. For a few hours things looked good with no duplications. Then I realised that a significant number of contacts were missing and they were now missing from Outlook.com too. This has clearly happened oin two stages because, although unfortunately both my computers synced up and so some contacts had been deleted across all devices, one computer has been off over the weekend so I have been able to copy the remaining contacts to a second account. EXTREMELY annoying. This deletion was most disappointing because that should not happen when merely disabling the sync on the phone. I also don’t understand why this has clearly happened in at least two stages. Only 212 contacts out of over 900 have survived this afternoon before I managed to recover about 600 from the offline machine (and even that is not the complete set).

I don’t think there is anything that Support can do about some of these aspects of the problem, but the developers need to work on the various interfaces and the routines that run on the various platforms – the need to play nicely together, especially as Windows 10 users no longer have the choice of a Windows Phone.

I would appreciate Supports view on the contact deletion though as having some cocked-up contacts is better than a considerable number being deleted.