Change orders are among the main sources of problems challenging timely completion of construction projects. The significantly needed conducive interaction among project participants to mitigate completion delay risk due to change orders is often hampered by interface problems. This article describes potential sources of interface problems and their role in affecting completion time of change order-challenged infrastructure construction projects in Indonesia. The identified sources then serve as inputs to formulate a systems thinking model of relational interface problems in change order-challenged projects. A survey of eleven important infrastructure construction projects was conducted to obtain data on the main sources of these interface problems and their severity indexes. A second survey was later conducted to perceive the most frequent causes of change orders, the influence of interface problem cause factors on the length of change order process and the influence of interface problem cause factors on the expediting capacity of a project team and ultimately induce a delay of project completion. The results of both surveys then served as inputs to a systems thinking structure showing the factors in a change order-challenged project. The study shows that contract, technical experience, management, coordination and financial aspects are the potential sources of interface problems in Indonesian infrastructure construction projects. In a change order-challenged project, these interface problems' sources will complicate the efforts to achieve the project's time objective. The study especially points out the role of contract documents' quality in increasing the likelihood and extent of change orders and the influence of workers' productivity in mitigating the negative impact of a change order.