Office 365 Calendar one way sync In outlook 2016 for Mac

Hello,

After more than half year without any issues, we recently started having problem with the calendar not syncing to the server only way to fix is to purge calendar and re-download from the server but meanwhile all the appointment that did not sync is lost and problem reoccurring after few days.

It happens only on Mac devices, I was not able to replicate the problem on PC or on the mobile phone

If I create test appointment on affected user iMac it will not sync to server but appointment created in OWA sync to the affected user computer.

If I delete test appointment in OWA it will not disappear from the Outlook.

Kind Regards

Bernard