outlook.com contacts will only sync one way with android and outlook app

I have added my hotmail.com account as exchange in outlook app on android (nexus 6).

Contacts sync one way only.

Problem:

1. Any new contact added via the android native contacts app to the "hotmail.com" account is deleted without warning on next sync.
2. Edits made to hotmail.com contacts in native android contacts app are overwritten and lost on next sync.

I have had this problem for more than 1 year. I have now spent about 50 man hours trying to find a solution.  Because the phone is unusable without the ability to add or edit contacts, I have been using my partners old iphone 5c, which syncs contacts both ways flawlessly but means I cant use my smart watch.

My hotmail account was "upgraded" to exchange some months back, but the result before and after is the same (after removing and re-adding of course)

I have spent probably 5 hours with MS support teams.  

1. First I tried the outlook android app  "in-app" support. They got me to reinstall outlook and my account, and checked various things were ok, then said there was nothing wrong with my setup, and it must be an issue with the account itself. They sent me to the MS account support eam.
2. The MS account support team said my account was fine, and it was nothing to do with them, and sent me to the desktop outlook support team.
3. The desktop account team sent me back to the account support team.
4. The account support team told me to go back to the android outlook in-app support team. they told me to get an apple phone instead.

So it looks like the 100 or so people who have the same problem have no support, and no solution, other than to switch to iPhone.