Preprint of a conceptual paper on hidden switching errors in quantum thought experiments. The paper argues that many well-known paradoxes arise not from internal inconsistency of quantum theory itself, but from silent transitions between incompatible mathematical descriptions, such as wave and particle models or probabilistic and factual descriptions. A simple labeling method is proposed to mark different reasoning tasks and make such transitions visible. The method is applied to the Frauchiger–Renner argument and to EPR/Klyshko-type scenarios. Full text available in the attached PDF.