I think it’s about time @jaslan and @skijumptoes got a proper mention (I’m still getting used to this forum). Thank you so much for your help, you have pointed me at doing some serious digging and I have finally cracked it!
It was @skijumptoes who came up with answer: Mono output from the CR. I did check that (honestly) but I think I must have been suffering from general brain/ear failure at the time. But I’ve made a useful discovery: changing VST Connections presets can switch CR between Mono and Stereo remotely! I never knew that was even possible.
I have also discovered a few settings I didn’t know about or had forgotten about so thanks to both of you for that too. None of them made any difference but I’m glad to know they’re there.
So, an embarrassing rookie error but you live and learn, eh? Such as it’s a crap mix (it’s very old, in my defence) and I’m going to have to do it again. It also explains why it sounds so bad on my (mono!) Bluetooth speaker and people’s phones. The clues were all there but I was stuck in the driver rabbit-hole.
AAAAaaargh…!
Thanks again, peeps, catch you on the ether sometime.
PS: that sure was weird indeed, @jaslan, about Alanis. Six degrees of separation they talk about, don’t they? I think that might be an exaggeration…