I have been working with both apple and microsoft since the release of 17.2 in decemeber. I've provided both organizations logs and data and video of the problem and it's alot of finger pointing right now.
I can confirm that 17.3 doesn't help the issue is still in there it seems to be around a policy in the MDM which cause the phone to bug, I'm hopeing with the amount of data I've sent and other people as well they will take it seriously but it's super hard to get an straight answer from either as now MS is telling me it's an apple problem and apple is telling me my ticket is still being looked into. 😞 if your clients have less then 1000 contacts it seems to work ok anyting who has more then 1000 contacts seem to be affected big time from total freezing or lost calls and even worse it kills the devices battery.