Having talked to support, it sounds like there is an issue with the ZRC-90 that the beta doesn't address, whereby the ZRC doesn't associate correctly (possibly due to some config in the z-wave dongle).
Backing up, then resetting the Vera (including Z-Wave network to a clean state, then adding the ZRC-90 works well with the new beta (it gets the correct JSON file etc) (although at this point you won't have any other devices associated!).
I then restored the backup, so I had my other devices, and re-adding the ZRC goes back to failing. So for now, I have the choice of re-starting my network from scratch, or a working ZRC-90.
Hopefully support will come up with a fix for the association issue.