Kinematic/Axis Interface state machine documentation (safe motion problem)

Is there a state diagram of how the different states move from state to state in the kinematic interface and the axis interface?

I would like to know the correct sequence for moving through these states.  I have an issue when the drives are put in STO that the state machine becomes unresponsive.   I cannot find a good explanation of how the transitions between states are supposed to be commanded.  The state machine appears to get lost, no longer controlling the drive states.  As of now, only a cold reset on the PLC will make it recover.  I am not sure if I am doing something incorrectly or not.