Imported files lose stereo and become squashed into mono

I’ve recently picked up a UA Apollo Twin Interface, and have been using lots of lovely UAD plugins with it. Of course, I can only use a certain number of plugins in one Cubase file before the DSP of the interface runs out, so I’ve split my mix into a few Cubase files (ie. drums, vox, master) in order to use as much DSP on parts that need them.

I export the files once happy with them, but when I import the exported wav files into the ‘master’ Cubase file, the files lose their stereo quality completely. Anything panned, or parts which sit in stereo (ie. ‘sound’ from L40 across to R60, covering that range) just become completely mono, and the mix console proves it. I’ve checked, and the wav files sound as I want them to before they’re imported into Cubase, so I must be missing something in the import settings!

Is there a way around this? I’d really really appreciate some help!

Windows 10
Cubase 9 Artist
UA Apollo Twin USB Interface

Cheers
Sam

Bump^^^

Really stuck with this, seems to be a simple problem, I hope there’s a simple solution!