onlineMeetings meetingAttendanceReport changes and contains invalid data

Question

I've created a integration with the OnlineMeeting API (beta) and the meetingAttendanceReport-endpoint. I've noticed that the data returned for the report has changed.

When I fetched the data 2021-08-19 it contained 4 participants in the meeting (with join date 2021-08-19), but when fetching the report right now there is only one participant that joined 2021-08-26 (7 days later).

I've also noticed that there is no meetingAttendanceReport for meeting that is "older" (like 5-6 weeks) is that expected?

When I try to fetch an older meeting I get this response:

System.AggregateException: One or more errors occurred. ---> Microsoft.Graph.ServiceException: Code: BadRequest
Message: Value cannot be null.
Parameter name: String
Inner error:
AdditionalData:
date: 2021-09-07T14:56:11
request-id: 17cdbf75-d8cb-40e8-8434-b667952d149c
client-request-id: 17cdbf75-d8cb-40e8-8434-b667952d149c
ClientRequestId: 17cdbf75-d8cb-40e8-8434-b667952d149c