Teams channel messages delta API returns HTTP 400 BadRequest

Hello,

We are encountering an unexpected error when calling the Microsoft Graph API endpoint:

/teams/{team-id}/channels/{channel-id}/messages/delta

This happens consistently for a specific Teams channel, which prevent us from retrieving incremental message updates using the delta query.

Request URL:

https://graph.microsoft.com/v1.0/teams/{team-id}/channels/{channel-id}/messages/delta?$deltatoken=<redacted-deltatoken>

Error Response:

HTTP 400
{
  "error": {
    "code": "BadRequest",
    "innerError": {
      "client-request-id": "<redacted>",
      "date": "2025-10-07T06:32:56",
      "request-id": "<redacted>"
    },
    "message": "UnknownError"
  }
}

Steps already tried (unsuccessful):

• Start a fresh delta query without the $deltatoken to obtain a new valid token
• Use the beta endpoint:

https://graph.microsoft.com/beta/teams/{team-id}/channels/{channel-id}/message/delta

Additional observation:

• If we add a filter condition such as

?$filter=lastModifiedDateTime gt <some-timestamp>

to skip messages before a certain time, the query works normally.

• This suggests that there may be one or more problematic messages within a specific time range that cause the API to fail with BadRequest.

Questions:

• Is this a known issue with the Teams channel messages delta API?
• Are there any recommended workarounds to avoid this error?

Thank you.