Contacts Sync from Exchange

I configured my corporate Exchange account on my iPhone 5s (iOS 9.2.1).

I chose to sync it in manual mode.

I have a couple af problems:

1. No issues for Calendar and Mail: every time I open one of these Apps it syncs data with Exchange server.

Not the same with Contacts: it seems to sync only after I restart iPhone or when I update something from the device. Is was different with older iOS version (6 or 7, I don't remember): also Contacts App updated data when I opened it.

2. On Exchange server I created a couple of subfolders into Contacts main folder (Customers and Providers): they seem not to be synced at all!

If I completely disable Contacts sync (so all local informations are deleted) and then enable it again, iPhone downloads also Contacts from subfolders, but during a normal update (eg when I add something into device) subfolders are not synced.

Thank you!