6996 ENT (SM 17). I reported before that on my mac I show multiple "My Contacts" listed. Yesterday looking at the calendar on my iPhone X to review my schedule I saw NO appointments at all from my SM 17 server. I checked that the calendar was enabled, I noticed it showed "My Calendar" about 7 times, very odd, and no appointment data. I went to the iOS accounts area and turned off the calendar, answered YES to delete all data on the device, then turned on the calendar again. I showed multiple "My Calendar" items and then it went to one, and after some time it synced again.

Something continues to be very odd and unreliable with your Active Sync system. I'm using EAS on the phone, as EWS has worked terribly on the mac I'm using carddav/caldav.