What does an error 500 in Apple Music mean?

I recently encountered error 500 when trying to add new playlists, with the option set to add playlisted items to my library. I haven't found any documentation for Apple Music error messages. What does an error 500 in Apple Music mean? **Update**: Adding new items directly to my library instead of via a playlist gives a more helpful error message, stating "These additions would exceed the Cloud Music Library limit of 100,000 songs". So I think error 500 probably means the same thing.