REST error when creating Communicate campaign

Summary:

Since the 25D release, we are seeing an "Error response during RestAction" message when viewing or creating Communicate campaigns in Redwood. This is happening with the seeded Communication Manager and Administrator roles, so I'm not sure if this is a missing privilege or something else.

I've already raised an SR, but in the meantime wondered if anyone has experienced this and found a solution?

Version (include the version you are using, if applicable):

25D