Trajectory control with singularity points. Trayectory TT2

This video shows the execution of a trajectory (TT2) by the 4dof reconfigurable robot. The TT2 trajectory has a simultaneous motion of 0.2m on the X_F axis, 0.1m on Z_F, while  the pitch angle rotates 15º and yaw angle rotates 59º:

In this trajectory (TT2) the robot reaches a singular point. You can see that when it is on the singular point, the robot wins (at least) one DOF, so the robot gets to lose control and it is possible to move the robot with a finger.