Sometimes Microsoft calendar event not generated in outlook calendar

We are using Microsoft Graph API for creating events in the outlook calendar using Android. It works well but now sometimes it doesn't create events in Outlook Calendar and it also receives event invitations Mail in Junk Email. After updating that event now all events create properly.

We encountered this problem two or three times but I couldn't figure out the problem.No errors were found on the front-end side as well as the backend side.

Can anyone please suggest why this is happening?

Finally, We figured out why it happened.

Microsoft permanently deletes an event from Outlook when an attendee declines that event.

So the thing happened that,

First Microsoft Attendee declined the event and then the organizer updated the event by adding only another attendee (no other changes like summary, dates, timezone, location, etc...). so in this case, Microsoft didn't create a new event in the calendar for that particular attendee who previously declined the event.

The event is created in that specific attendee's calendar if the organizer made another change (like summary, dates, timezone, location, etc...) to that event.