Oculus runtime blocking Steam online subsystem

I am trying to set up a network game using SteamOnlineSubsystem (using app id 480 - “spacewar” ) and SteamVR.
My colleague is using a Vive and myself a Oculus headset.

Everything worked fine a couple of months ago (using UE 4.16) We were able to connect to each other’s sessions and interact.

Now after a couple of months development pause we upgraded to UE 4.18 and suddenly no sessions were found anymore. While trying to narrow down the problem we also started old 4.16 builds and ran into the same issue. The same builds that were running smoothly a couple of months ago couldn’t find the sessions of my colleague anymore and he couldn’t find mine.

My logs are throwing this warning now:

LogOnline: Display: STEAM: Loading Steam SDK 1.39
LogOnline: STEAM: Steam User is subscribed 1
LogOnline: STEAM: [AppId: 480] Client API initialized 1
LogOnline: Verbose: STEAM: Initializing Steam Game Server IP: 0x00000000 Port: 7777 SteamPort: 7778 QueryPort: 27015
LogOnline: STEAM: [AppId: 480] Game Server API initialized 0
LogOnline: Warning: STEAM: Failed to initialize Steam, this could be due to a Steam server and client running on the same machine. Try running with -NOSTEAM on the cmdline to disable.
LogOnline: Display: STEAM: OnlineSubsystemSteam::Shutdown()
LogOnline: Warning: STEAM: Steam API failed to initialize!
LogOnline: Display: STEAM: OnlineSubsystemSteam::Shutdown()
LogOnline: Unable to create OnlineSubsystem module Steam

As the warning didn’t appear at my colleague who’s using a Vive I had the feeling the culprit might be connected to Oculus. I killed all Oculus processes (OVRServer_x64.exe) and services in the task manager and voila, we were finding each other’s sessions again and were able to connect. Obviously without any of the processes running my Oculus HMD didin’t work anymore which is a problem when you are developing a VR prototype.

It seems that recent changes in the Oculus runtime are blocking the Steam OnlineSubsystem Game Sever API.

Did anyone here encounter a similar problem?
Any help would be highly appreciated.