The Common Variability Language (CVL) allows deriving new products in a software product line by substituting fragments (placement) in the base model. Relations between elements of different placement fragments are an issue. Substitutions involving interfering placements may give unexpected and unintended results. However, there is a pragmatic need to define and execute fragments with interference. The need emerges when several diagrams are views of a single model, such as a placement in one diagram and a placement in another diagram reference the same model elements. We handle the issue by 1) classifying interfering fragments, 2) finding criteria to detect them, and 3) suggesting solutions via transformations. We implement our findings in the tooling available for downloading.