Help needed to track down inconsistent metadata setting

[haggis999]

I have just realised that one of my opera CD box sets is not being displayed by MinimServer 2 in the same manner as all my other opera recordings. My browsing selections are as follows, using the attached MinimServer settings.

Classical library > Sub-Genre = Opera > Composer = Mozart

This presents me with the thumbnails for 5 operas by Mozart. If I tap on 4 of these thumbnails, I am taken to a page displaying just that selected thumbnail. I can then choose to make a long press to get 'Play/Queue next/Queue last' options or I can just tap it to open up a full list of all the tracks. This is the expected behaviour. The 5th thumbnail is for Idomeneo. If I tap that I am taken straight to the track listing, which is not what I want.

So far, I have failed to see any difference in the metadata settings for Idomeneo compared to the other 4 Mozart operas, but something must be different. Can anyone suggest what that might be?