This issue is now resolved, please see updated blog post:
We’ve received reports that some Blackboard Ultra assessments created via the integration with SITS/eVision – specifically, the BBOther or Turnitin submission types, which use calculated columns – are being labelled in the Gradebook as ‘Non-markable items’.
This does not affect the functionality – marks can still be mapped and extracted by the normal method. However, it may cause confusion in the marks view, where these columns show as ‘Non-markable items.’
Anthology is currently investigating the issue. We apologise for any inconvenience and will provide updates as soon as we have more information.