Many "Accepted" messages sent by Microsoft365 when we updated a event using Graph API

Question

Our product (SaaS) has a function that connects to Microsoft365. When a user creates an event with meeting rooms on Outlook, our service detects it and writes some messages in the event using Graph API.

On March 30th, 2022, Microsoft365 suddenly started sending many emails. They describe that the meeting room accepted the request. It's ok if we receive an email once, but we receive them about 5 to 10 times in some minutes.

Without our service, we don't receive many emails, only once. We didn't update our service on that day, so we have been confused about it.

We got audit logs from our Microsoft365 admin, and it shows that the event was updated many times by the Microsoft365 server itself (not by our service).

We are wondering what is happening. Does someone have any ideas?

Thanks.