I have no experience with the exD bridge, but if you’re connecting with Dual AES (that’s what’s indicated in your photo) and the channels are not reversed at other sample rates then the problem is likely in the way that the exD handles DXD data.
I doubt the issue is in Roon’s upsampling algorithm as I use that feature a lot in certain configurations and have never encountered a channel reversal.
Thanks Andrew / Peter for your response, much appreciated. Yes I would suspect the problems lies on my bridge (exD), as Antipodes has confirmed that there would be nothing in the Antipodes software which would cause this, and my dCS is working properly for all other sample rates … hence… I guess I know where to look now.