Outputs configured in I/O setup not available to select as track sends/outputs

[Stuart@YM]

Hi all

I'm experiencing an issue whereby I/O settings are behaving strangely upon opening new sessions.

I created a new stereo Output called Ext Mixer (outputs 5-6) which, initially, are selectable as outputs or sends from audio tracks. So, all good.

However when I open a new session, the I/O doesn't change but the outputs/sends are no longer available from the audio track drop-down menus...

If I delete the I/O and start again, creating the outputs etc from scratch, they then become available again from the drop-down menus but doing that every time a new session is opened would be very inconvenient.

I have attached screenshots showing the I/O and the track dropdown menus.

Any suggestions v much appreciated.