GET all my calendars not working anymore with personal account

[KaiWalter]

Describe the bug
A clear and concise description of what the bug is.

To Reproduce
Steps to reproduce the behavior:

1. go to Graph Explorer
2. sign in with personal account (not work account)
3. use GET https://graph.microsoft.com/v1.0/me/calendars
4. Run query

Expected behavior
All calendars available to that account are listed in the response.

Screenshots
Actual response with Graph Explorer and .NET GraphServiceClient:

Headers:

{
    "cache-control": "private",
    "client-request-id": "50a57a4f-f51c-b130-9fdc-19dec533c3d2",
    "content-type": "application/json; odata.metadata=minimal; odata.streaming=true; IEEE754Compatible=false; charset=utf-8",
    "request-id": "9f256163-932a-4cf6-a4b4-2bd1b6ee6599"
}

Body:

{
    "error": {
        "code": "ErrorInternalServerError",
        "message": "An internal server error occurred. The operation failed."
    }
}

Desktop (please complete the following information):

• OS: Windows 11 and NixOS
• Browser Edge and Brave

Additional context
This seemed to have worked - at least with the .NET application until May 31st (?)

[JeroenBer]

Seems to be duplicate with #3860 and #3861

[ajtruckle]

@JeroenBer It looks like they are the same. MS please come to the rescue of your users. 🙏