Issue with MgSecurityCaseEdiscoveryCaseMember

[SWeppler-WA]

Describe the bug

I am an eDiscovery Manager and I am trying to use New-MgSecurityCaseEdiscoveryCaseMember to add people to an eDiscovery case.
Since SDK version 2.35.1 this worked fine. On 5/4/2026 it stopped working. Status: 401 (Unauthorized) ErrorCode: UnknownError

I asked an eDiscovery admin to test the command and it worked for him. This appears to be related to me being a Manager instead of an Admin.
I attempted to reproduce the error using Graph Explorer but did not find a resource for ../securityMembers

If I should be able to use Graph Explorer to reproduce the error please advise on finding a resource.

Expected behavior

no error

How to reproduce

1. Configure a user as an eDiscovery Manager role

2. Connect to scope "eDiscovery.ReadWrite.All"

3. Identify a case and set $ediscoveryCaseId

4. Code snip
   $params = @{
   recipientType = "user"
   smtpAddress = "user@microsoft.com"
   }

   New-MgSecurityCaseEdiscoveryCaseMember -EdiscoveryCaseId $ediscoveryCaseId -BodyParameter $params

SDK Version

2.37.0

Latest version known to work for scenario above?

all known versions stopped working on 5/4

Known Workarounds

Use the purview portal. No known powershell work-arounds.

Debug output

Click to expand log

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### Configuration

Name                           Value
----                           -----
PSVersion                      7.5.1
PSEdition                      Core
GitCommitId                    7.5.1
OS                             Microsoft Windows 10.0.22631
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Windows 11 x64

### Other information

_No response_