Bot call automatically terminated after trying to establish

Describe the issue
I am testing PsiBot example. I am running it with .NET 6.0. I got joinCall working, then first /api/calling to establish, but seconds later I got another /api/calling to terminate the call. So the bot never joins the meeting. The message from second /api/calling is "Server Internal Error. DiagCode: 500#1203002.@"

Code Snippet

Expected behavior
The bot should join the meeting.

Graph SDK (please complete the following information):

 <PackageReference Include="Microsoft.Graph" Version="5.38.0" />
<PackageReference Include="Microsoft.Graph.Communications.Calls" Version="1.2.0.10563" />
<PackageReference Include="Microsoft.Graph.Communications.Client" Version="1.2.0.10563" />
<PackageReference Include="Microsoft.Graph.Communications.Common" Version="1.2.0.10563" />
<PackageReference Include="Microsoft.Graph.Communications.Core" Version="1.2.0.10563" />
<PackageReference Include="Microsoft.Psi.Imaging.Windows" Version="0.19.100.1-beta" />
<PackageReference Include="Microsoft.Skype.Bots.Media" Version="1.30.0.19-preview" />
<PackageReference Include="Microsoft.Graph.Communications.Calls.Media" Version="1.2.0.10563" />

Call ID
2025-06-10T13:50:49.1743446Z call-id: 03005e80-cef6-457d-ade2-7341b0ce39d5
2025-06-10T11:46:49.2201324Z call-id: 34005980-c729-4591-bd8f-07d89d282c55
2025-06-10T01:41:08.8033901Z call-id: 07005c80-537c-4ac6-8c9b-b3b43b1f99a5

Logs
Second /api/calling response:
{ "@odata.type": "#microsoft.graph.commsNotifications", "value": [ { "@odata.type": "#microsoft.graph.commsNotification", "changeType": "deleted", "resource": "/app/calls/07005c80-537c-4ac6-8c9b-b3b43b1f99a5", "resourceUrl": "/communications/calls/07005c80-537c-4ac6-8c9b-b3b43b1f99a5", "resourceData": { "@odata.type": "#microsoft.graph.call", "state": "terminated", "resultInfo": { "@odata.type": "#microsoft.graph.resultInfo", "code": 500, "subcode": 1203002, "message": "Server Internal Error. DiagCode: 500#1203002.@" }, "chatInfo": { "@odata.type": "#microsoft.graph.chatInfo", "threadId": "19:meeting_YWI3MGVlM2EtNGVlNS00NzIxLTg0MzgtZDE0OWVmNmI1ZTg0@thread.v2", "messageId": "0" }, "meetingInfo": { "@odata.type": "#microsoft.graph.organizerMeetingInfo", "organizer": { "@odata.type": "#microsoft.graph.identitySet", "user": { "@odata.type": "#microsoft.graph.identity", "id": "ec183066-03f4-4c44-b620-8696f70e75d8", "tenantId": "15e71edc-5c3f-4c0f-b430-20a12d1fe785" } } }, "callChainId": "2217848d-6b0f-429a-bc6f-74d473f80fd8" } } ] }

Additional context
I got PsiBot working in .NET Framework 4.8, so there should be no issue with certificate, domain, and app registration. I got the error after upgrading to .NET 6.0.

Start with the PsiBot example and the /api/calling flow, comparing its .NET 6.0 setup with the reported working .NET Framework 4.8 setup and the listed package versions. Use the second /api/calling notification and termination code 500#1203002 as the failure point. Done means the bot joins the meeting and is not automatically terminated.