Stuck in "Waiting for <game>" with Vive Pro Eye after calibration (Unity)

[Dutchottie]

I've got issues with SteamVR displaying the floating Unity logo with my application's name and Waiting...
Normally this screen only is visible when loading the application.
Issue 1 - Unity Build version using Vive Pro Eye no eye calibration
Unity 2020.3.3, OpenXR 1.0.3, XR 4.0.5, Tobii SDK2.0.0.174 and SRanipal 1.3.3.0, Windows 10
I'm using the
> XRGeneralSettings.Instance.Manager.InitializeLoader();
> XRGeneralSettings.Instance.Manager.StartSubsystems();
to make sure everything starts.
However, when starting the executable the SteamVR image first goes to a blueish sky with the Unity logo, then the floating windows pops up with my application's name and Waiting for... underneath it. It does not disappear and so the application never gets going in the Vive.
When I run this same config in the Unity editor it does work!
Issue 2 - Editor version using Vive Pro Eye with eye calibration
Unity 2020.3.3, OpenXR 1.0.3, XR 4.0.5, Tobii SDK2.0.0.174 and SRanipal 1.3.3.0, Windows 10
Now I start (after a key press) the build-in eye tracking calibration. The Unity application starts correctly. Whe I press the C-key the Vive Pro Eye calibration utility is started (in SteamVR) and runs fine. When done I pop back into a black surrounding (that's the application's scene) but with the floating SteamVR windows telling me to wait for the application.
The application does run in the background (interaction works and I hear the audio playing) but there is no image in the Vive.

I've never had any issues with the Vive Pro Eye and the eye tracking or SteamVR before using the new XR plugin with the OpenXR package.