mmpbsa with quasi-harmonic entropy approximation error

gistfile1.txt

Loading and checking parameter files for compatibility...
mmpbsa_py_energy found! Using /Users/david/bin/amber14/bin/mmpbsa_py_energy
cpptraj found! Using /Users/david/bin/amber14/bin/cpptraj
Preparing trajectories for simulation...
1 frames were processed by cpptraj for use in calculation.

Running calculations on normal system...

Beginning GB calculations with /Users/david/bin/amber14/bin/mmpbsa_py_energy
  calculating complex contribution...
  calculating receptor contribution...
  calculating ligand contribution...

Beginning quasi-harmonic calculations with /Users/david/bin/amber14/bin/cpptraj
Error: DataSet_Modes: bad eigenvalue 0 = 0.000000
Error: in Analysis # 0
Error: DataSet_Modes: bad eigenvalue 0 = 0.000000
Error: in Analysis # 1
Error: DataSet_Modes: bad eigenvalue 0 = 0.000000
Error: in Analysis # 2
  File "/Users/david/bin/amber14/bin/MMPBSA.py", line 104, in <module>
    app.run_mmpbsa()
  File "/Users/david/bin/amber14/lib/python2.7/site-packages/MMPBSA_mods/main.py", line 218, in run_mmpbsa
    self.calc_list.run(rank, self.stdout)
  File "/Users/david/bin/amber14/lib/python2.7/site-packages/MMPBSA_mods/calculation.py", line 82, in run
    calc.run(rank, stdout=stdout, stderr=stderr)
  File "/Users/david/bin/amber14/lib/python2.7/site-packages/MMPBSA_mods/calculation.py", line 375, in run
    Calculation.run(self, rank, stdout=self.output)
  File "/Users/david/bin/amber14/lib/python2.7/site-packages/MMPBSA_mods/calculation.py", line 157, in run
    self.prmtop))
CalcError: /Users/david/bin/amber14/bin/cpptraj failed with prmtop com.top!
Exiting. All files have been retained.