RPC_S_SERVER_UNAVAILABLE error when connection through Windows 2019 sshd

We are trying to use certreq.exe to issue SSL certificates. certreq.exe uses RPC against a Microsoft CA

Setup: Linux-Client -> Windows 2019 Server where we can execute certreq.exe (*)-> Microsoft CA Server

This works

• locally
• via RDP using cmd or powershell
• via scheduled task

This does not work if executed via sshd running on a Windows 2019 Server:

certreq -q -config "xyz" -attrib "xyz" -submit "xyz.csr"
Certificate Request Processor: The RPC server is unavailable. 0x800706ba (WIN32: 1722 RPC_S_SERVER_UNAVAILABLE)

There is no difference if this user has local admin privileges on (*) or not. The error message is always the same

Are there any documented limitations regarding RPC/EPM (Port 135) or is this a bug?

"OpenSSH for Windows" version
7.7.2.2

Server OperatingSystem
Windows Server 2019 Standard

Client OperatingSystem
SLES 12 SP5, OpenSSH 7.7p2

What is failing
RPC call is failing, see error message from certreq above

Expected output
No error output, succesful RPC

Actual output
The RPC server is unavailable. 0x800706ba (WIN32: 1722 RPC_S_SERVER_UNAVAILABLE)

The issue names no repository files or tests. Start by reproducing the certreq command through Windows OpenSSH and compare it with local, RDP, and scheduled-task execution; done means determining whether the RPC failure is a documented limitation or an actionable Win32-OpenSSH bug.