Despite the body of evidence suggesting that contracts can complement social controls, much remains to be learned about situations where complementarity is not evident. The emerging contingency perspective on complementarity provides insights into the complexity of the contract-trust interplay, but little theoretical guidance exists suggesting how this interplay can be influenced such that dysfunctional relationships lacking trust can be transformed. This longitudinal study of three problematic relationships in a complex engineering projects setting exposes a duality in formal coordination mechanisms that has a polarising effect on trust. For dysfunctional relationships to become collaborative, coordination mechanisms need to address impediments to mutuality, enabling new relational norms to develop, which in turn disrupt negative trust cycles, enabling relationship repair.