Tendon-driven manipulators have interesting properties such as reduced inertia and a better behavior w.r.t. physical interactions through the possible modulation of their stiffness. A 2-tendon-driven manipulator inspired by the bird neck is studied in this paper. The manipulator is remotely actuated with two tendons and only one output variable can be controlled. When applying a computed torque control, we observe that the control of one joint is stable but the control of the other joint is unstable. The goal of this paper is to provide a physical interpretation of this behavior. Instability is explained through the study of the dynamics in open-loop. Experiments are conducted that confirm the aforementioned behavior.