MotionInterpolator interpolate method return value

hello together,
i have created 9 targets in the motion interpolator, which I now want to run through in 0.5s steps and check for axis value overruns. I have assumed that the boolean return value of the method motionInterpolator.Interpolate(time, ref timeSlicePos); indicates whether the interpolation was successful. In my case, the return value in the code below is always false. The return value is not exactly described in the help (see screenshot). Am I doing something wrong or am I interpolating the return value incorrectly?

Thanks for your support.

IMotionTarget timeSlicePos = robot.RobotController.CreateTarget();

for (double time = 0; time < cycletime; time += 0.5)
{
bool success = motionInterpolator.Interpolate(time, ref timeSlicePos);
if (success == true)
{
//Good
var jointValues = timeSlicePos.GetAllJointValues();
}
else
{
//Problem
}
}