From: RUN_MFIX
Error 1001: Unable to open input data file: fluid_bed_tfm_3d_1019.mfx^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@^@
....
Those NUL characters after the file name should not be appearing. I do not know exactly what caused this, but I suspect an incompatibility with either your Fortran compiler or OpenMPI. I see that you are using
gfortran: GNU Fortran (GCC) 4.8.5 20150623 (Red Hat 4.8.5-36)
openmpi: Intel(R) MPI Library for Linux* OS, Version 2018 Update 4 Build 20180823 (id: 18555)