I'm using EAS on a variety of devices, no issues on my phone but I'm getting sync issues on the desktop.

When an account is first configured (all this applies equally within Outlook 2016 and the default win 10 mail app) it'll work perfectly, email sync is very quick, things go to the right folders, contacts/calendar sync up and down no problem.

After a while however things start to go wrong, some emails (but not all) will get stuck in the wrong folders and contacts no longer sync upwards. Everything seems to sync downstream properly so I get all my email (even though it won't change folders) and changes made to contacts will come down. If I delete then reconnect the account it'll work for a while and then start to display the same behaviour.

I have the same problems across a range of devices, is this something caused by Microsoft and I'm just going to have to accept it and stick with the web client?