That seems like a bug to me. File it… The GUI sums this on its own I think, and there the local state gets reduced when a folder is paused, as that folder “disappears” from the summary.
I think that’s more of a limitation than a bug: We do remove paused folders from the model state, thus a call to /rest/db/completion checks if there is state, sees there is none, checks config and sees it’s paused → error. We’d have to either not remove the FileSet from model for paused folders or create one (potentially expensive) on API calls.
To mirror the GUI behaviour we’d simply skip paused folders in the iteration/calculation. I don’t think it makes sense to talk about the completion status of paused folders…