I saw that about the error but was assuming the application(s) all worked reliably and then all of a sudden went south?

What could have happened in that timeframe?

Was there a move of development code to the production server? Perhaps it wasn't fully tested?

That might account for the mutating error, un-tested development code being put into the production database, but I don't know how that would corrupt your all_objects view in the data dictionary.

Do you know what else was happening in the database at the time it failed?