The volume of large-scale, digitised, and born-digital historical text corpora has seen a significant surge in recent years. While this growth opens up new avenues for innovative research, it simultaneously presents challenges in terms of source and data criticism. This poster, using the Open Discourse Corpus—a structured collection of all speeches delivered in the German Bundestag since 1949—as a case study, unveils a novel method of source and data criticism. Through a sample study conducted on a gold standard corpus, it is revealed that the corpus has substantial structural deficiencies, thus restricting its suitability for historical research. This poster is part of the poster session at the Digital History Tagung 2023 in Berlin.