:bug: VaryRun random seed does not produce the same input files

## Describe the bug

When specifying a `SEED` for a VaryRun, the input files created are not the same which is unexpected since specifying a SEED should ensure that they are. 

## Steps to reproduce

Run VaryRun twice and compare the first input files created. 

## Expected behaviour

The two input files are the same if a SEED is specified
