Momentum Change is not a unit vector error?

Particles, Track, Event, Run and Biasing
1

I’m getting an error when I use a inverse CDF sampling in energy that I don’t see using a flat distribution. The error is:

  G4ParticleChange::CheckIt  : the Momentum Change is not unit vector !!  Difference:  1
neutron E=2.51889 pos=-0.0902091, -0.0902091, 9.99919
      -----------------------------------------------
        G4ParticleChange Information  
      -----------------------------------------------
        # of 2ndaries       :                    0
      -----------------------------------------------
        Energy Deposit (MeV):                    0
        Non-ionizing Energy Deposit (MeV):                    0
        Track Status        :                Alive
        True Path Length (mm) :                    0
        Stepping Control      :                    0
    First Step In the voulme  : 
        Mass (GeV)   :                    0
        Charge (eplus)   :                    0
        MagneticMoment   :                    0
                :  =                    0*[e hbar]/[2 m]
        Position - x (mm)   :                -90.2
        Position - y (mm)   :                -90.2
        Position - z (mm)   :                1e+04
        Time (ns)           :                    0
        Proper Time (ns)    :                    0
        Momentum Direct - x :            4.66e-310
        Momentum Direct - y :            3.46e-323
        Momentum Direct - z :            1.35e-306
        Kinetic Energy (MeV):                 2.52
        Velocity  (/c):               0.0731
        Polarization - x    :                    0
        Polarization - y    :                    0
        Polarization - z    :                    0
        Touchable (pointer) :       0x55d2a86ee2e0
RuntimeError: *** Event Must Be Aborted ***
*** G4Exception : TRACK003
      issued by : G4ParticleChange::CheckIt
momentum, energy, and/or time was illegal

I don’t know what this error is. I’m generating my energy by:

G4float energy = interp(G4UniformRand(),cdf,energyVector);

which generates energy in MeV that ranges from 0.25 to 15 MeV. If I generate energy as:

G4float energy = 0.25 + G4UniformRand() * (15 - 0.25);

I don’t get the error. But I’ve checked all the energies and they’re all legal, I.E. no negative energy and no zero energy. What is causing the error?