Thanks, I wasn’t aware of AVLR so will give that a try over their weekend.
I did get a response from Zendesk with the following ‘We recommend using Windows Mixed Reality with your headset rather than Steam VR.’. I don’t believe this is feasible with the Pico 4 but there are a number of troubleshooting steps on their reply so I’ll go through it all anyway in the hope it somehow rectifies the issue.