Error when translating openfermion FermionOperators

[NRoshani]

when running the following code

import fqe
from openfermion.ops import FermionOperator


ket = fqe.Wavefunction(param=[[4, 0, 4]])
coeff = ket.get_coeff((4,0))
coeff[1][1] = 1
ket.set_wfn(strategy="from_data", raw_data={(4, 0): coeff})
ket.normalize()

ops = FermionOperator('6^ 4^ 4 6',0.5)
ops += FermionOperator('6^ 5^ 5 6',0.5)
ops += FermionOperator('7^ 4^ 4 7',0.5)
ops += FermionOperator('7^ 5^ 5 7',0.5)

ops_fqe=fqe.get_hamiltonian_from_openfermion(ops)
result = fqe.expectationValue(wfn=ket, ops=ops_fqe)

on gets following error

 line 289, in apply_diagonal_coulomb
    _apply_diagonal_coulomb(data, self._core.string_alpha_all(),
  File "src/fqe/lib/_fqe_data.pyx", line 557, in fqe.lib.fqe_data._apply_diagonal_coulomb

However, when changing the operator to

import fqe
from openfermion.ops import FermionOperator


ket = fqe.Wavefunction(param=[[4, 0, 4]])
coeff = ket.get_coeff((4,0))
coeff[1][1] = 1
ket.set_wfn(strategy="from_data", raw_data={(4, 0): coeff})
ket.normalize()

ops = FermionOperator('2^ 0^ 0 2',0.5)
ops += FermionOperator('2^ 1^ 1 2',0.5)
ops += FermionOperator('3^ 0^ 0 3',0.5)
ops += FermionOperator('3^ 1^ 1 3',0.5)

ops_fqe=fqe.get_hamiltonian_from_openfermion(ops)
result = fqe.expectationValue(wfn=ket, ops=ops_fqe)

it suddenly works. My guess something in fqe.get_hamiltonian_from_openfermion causes the issue but I could be wrong.