This is most likely a security permission issue. In case, 10221792, the field throwing this value was a Date Added field. We found that this field was a custom field of the clients.
We resolved this by adding permission to the user for the query view that was used for the customization. This can also be resolved by swapping out the field being used to one that the user has privileges to already.
To determine where the field was pulled from follow these steps:
1. Go to Marketing and Communication, Marketing Efforts, Export tab
2. Right click the appropriate export and select edit
3. Click to select the export definitions and click edit
4. Find the problem field on the right and locate where this value was pulled from on the left