Paradox theory often overlooks how (inter)organizational paradoxes interact and evolve within a processual context, both conceptually and empirically. This study delves into such 'knotting' by examining coopetition for sustainability, wherein competitors collaborate to address simultaneously economic, environmental and social concerns. We introduce a novel conceptualization of knotted paradoxes through the lens of system dynamics (SD). Within this SD framework, a knotted paradox is portrayed as a complex dynamic system characterized by contradictory cause-effect interactions forming intertwined balancing and reinforcing causality loops. This perspective facilitates a systemic understanding of the complex and dynamic nature of knotted paradoxes. We apply our conceptualization to explore an in-depth case study of how seven construction and housing firms collaborate and compete to plan a new sustainable residential area in a Swedish city. By constructing causal-loop models we examine how knotted coopetition and sustainability paradoxes exacerbate and mitigate each other, oscillating in their dominance through various processes over time. Through our analysis we distinguish three patterns of vicious cycles indicative of dysfunctional paradox evolution: Fading, Accelerating, and Mixed dynamics.