:bug: `--mfile` arg does not work as expected

[clmould]

Describe the bug

The --mfile argument when running PROCESS is not working as expected

Steps to reproduce

process -i path/to/IN.DAT --mfile TEST_MFILE.DAT

Expected behaviour

Running PROCESS as above should write the MFILE to your current working directory with the specified name (TEST_MFILE.DAT in this case), but it doesn't do this

Evidence

Environment

• OS:
• Version:

Additional context