This is kind of partly a blender problem. In that old scenes can't easily be updated to new nodes: Nodes are set up when they are added to the scene and can't really be upgraded.
For the most part we try to make things backwards compatible, but for now it seems like a fairly easy workaround to create a new uber node?
Thanks for the explanation that it's a Blender thing.
The difficulty with it just not working or spitting out "ERROR" on the viewport is that you have absolutely no idea which node (and there could be 10s or 100s of nodes in a scene) to actually replace... and it could be all of them you'd have to re-create (there's no copy this node settings, paste node settings function?). A lot of fiddly settings to transfer over one by one manually.
It would be great if breaking changes between Node versions could have a default applied and some kind of notification as to which material has an old node that needs replacing? It's probably not possible if it's a Blender issue.
I think as of RPR v1.7 250 on macOS this bug is FIXED. Thank you.