PR Summary

Resolves #459

Context

Since Get-Unique only works on sorted lists, this check was not sufficient to ensure that no items were repeated.

Changes

Replace instances of Get-Unique with Select-Object -Unique which does not require the list to be sorted first.

Checklist

• Pull Request has a meaningful title.
• Summarised changes.
• Pull Request is ready to merge & is not WIP.
• Added tests / only testable interactively.
  • Make sure you add a new test if old tests do not effectively test the code changed.
• Added documentation / opened issue to track adding documentation at a later date.