Investigate and fix scan x failure

[clmould]

Description

Closes #3071 and re-enables integration test test_scan which was previously being skipped due to this issue

Checklist

I confirm that I have completed the following checks:

• I have justified any large differences in the regression tests caused by this pull request in the comments.
• I have added new tests where appropriate for the changes I have made.
• If I have had to change any existing unit or integration tests, I have justified this change in the pull request comments.
• If I have made documentation changes, I have checked they render correctly.
• I have added documentation for my change, if appropriate.

[timothy-nunn]

Looks good Clair, this was a really weird problem! Cheers