outlook – Office 365 Win Add-in: Cannot get the custom property of a exception meeting through Office.js API

In my Outlook Add-in, i try to call Office.js API to save some information for a meeting. According to MSFT docs, i use Office.loadCustomPropertiesAsync to do it.

My case is:

  1. Create a series meeting and use Add-in to set a custom property.
  2. Invite some attendees and send it.
  3. Change one instance into exception and open it.
  4. Open Add-in to get the custom property which i saved before.

My expect result is that Add-in can get it. But actually, it returns null. Also, it works well when i open an occurrence or the whole series meeting.

Here is my sample code:

Office.context.mailbox.item.loadCustomPropertiesAsync(function(asyncResult){
  var customProps = asyncResult.value;
  console.log('property = '+JSON.stringify(customProps));

  var myProp = customProps.get("myProp");
  customProps.set("otherProp", "value");

  customProps.saveAsync(function(result){
     console.log('save result'+JSON.stringify(result));
  });
});

And my Outlook version is
enter image description here

This issue just occurs in the latest Win Outlook(After monthly channel 2005). It works well in Office Online and Mac Outlook.