Are you sure that it’s the Pro version that you are using ? I have a problem imagining a project with more than 256 Group channels… Beside this, check your memory usage, disk available space, and so on. Seems to me that, if you are actually using the Pro version, it’s probably a system related issue.
I do have 256 group channels.
My template is pre-mixed and require a routing system a bit complex.
Also for a year or so I’ve been composing all my pieces in one and only project.
It looks like it’s time to reconsider my system though…
Steinberg might want to reconsider this limit. I would think this would be enough too, but Simon Franglen, composer of Avatar: The Way of Water, apparently moved from Cubase to Pro Tools due entirely to the 256 group channel limit: