Deterministic test for Jastrow(backflow) optimization is failing with a several number of coefficients.

**Describe the bug**

I've been working with deterministic test for jastrow(backflow) optimization and found that deterministic test is failing with a several number of coefficients in different machine.

Test was done in workstation, theta, and summit (CPU) using develop version with last commit (f46901f01736950c75203f37ec701aa44aa78841) on May/19/2021. Only J1 is used for the test.

Optimized J1 is identical up to 3 parameters. (det_qmc_short_opt_3.in.xml)

Workstation : 1.021369511 0.916486567 0.8654997938
Theta : 1.021369511 0.916486567 0.8654997938
Summit : 1.021369511 0.916486567 0.8654997938

But if number of coefficient is increased to 5, they are giving all different values. (det_qmc_short_opt_5.in.xml)

Workstation : 2.95646542 -2.478173825 -4.360350896 -3.72100857 -2.081630639
Theta : -1.215235277 -2.132996212 -1.642853768 -1.823485461 -0.9572376071
Summit : Fatal Error. Aborting at Invalid Matrix Diagonalization Function!

With the choice of random seeds, it is giving different errors that could be related with this issue.

1. Fatal Error. Aborting at Invalid Matrix Diagonalization Function! (summit : det_qmc_short_opt_5.in.xml)
2. Fatal Error. Aborting at QMCHamiltonian::evaluate component NonLocalECP returns NaN (theta : det_qmc_short_opt_5_err.in.xml)
3. ERROR Safeguard failure: checkConfigurations variance out of [0.5, 2.0] * reference! Please report this bug. (theta : det_qmc_short_opt_5_err_2.in.xml)

**To Reproduce**
Run with single mpi/thread

[archive.zip](https://github.com/QMCPACK/qmcpack/files/6517215/archive.zip)

**Expected behavior**
Pass deterministic test

**System:**
Workstation(intel Xeon), theta, summit

**Additional context**
Add any other context about the problem here.