Some examples were: wordnets with no synsets, senses and synsets having different parts of speech, synsets with no part of speech, examples or definitions consisting of empty strings, different projects interpreting the directions of relations differently, definitions in unknown languages, projects including the PWN definitions, among others.
the new OMW system keeps adding an increasing number of extra checks on the content of uploaded wordnets, which warn the uploader of any problems before any upload is possible.