The disadvantage of this model is that it is difficult to check progress because there is a possibility that at one point three or four active phases are possible. In addition to this, there are still some dependencies between stages that are the same as in the traditional model. These dependencies can further complicate the project with a large phase overlap, and there may be a need for the development team to go back to the previous phase to define it in detail, leading to a significant delay.
This problem can be solved by setting finite metrics for each phase. Despite these shortcomings, this model is widely used in the software-manufacturing industry.