…on further investigation, it looks like my problem might be that Battery 3 isn’t showing up as a VST in my mixer. I can see the MIDI track, but not the VST output.
Edit 2 - I think I’ve realised what’s going on - this is a side-effect of the (in my opinion the STUPID) option where adding VSTs by default will add the VST to the MIDI track you are working on (rather than adding a ‘rack’ VST) which results in a situation where you cannot add multiple MIDI tracks pointing to the same multi-channel VST - but in this case, any automation you add to such a VST doesn’t show up as one would expect when choosing ‘Show all used automation’ - one must right-click on the MIDI track involved and choose ‘Show automation’.
This results in problems where for example if you need to ‘select all’ and move all tracks + automation to the right to make space for an intro, but the stupid MIDI instrument tracks do not show their automation properly.
I honestly couldn’t imagine how adding VSTs by default to a MIDI track could get any worse, but here we are.