UI moves based on different Vive HMD

I have published a build from Unity 2019.1.0f2 running on the Vive Pro.
The build has various UI HUDs that appear during the game. These canvasses are set "Screen Space - Camera" and Render Camera is the Steam "VR Camera".
This runs perfectly from the Unity editor and also in the published build.
When I run this on the Vive (not Pro) the UIs do not appear.
Debugging back in Unity shows the UIs to be in a closer space to the Vive, so nothing appears. Plug the Vive Pro back in and all is good?

With the Vive Pro plugged in the canvas originates at Z0.994. At runtime this moves to Z-5.264.
With the Vive plugged in the canvas again originates at Z0.994. At runtime this only moves to Z-1.066!
So, the issue is somehow the recognition of the different headset and the amount the canvas moves.

Any ideas, apart from scripting around it? I have logged this with Steam on Github.