Inherited value missing from extract

Summary:

Four records out of thousands in an extract have an inherited property showing no value ("") when the value looks correct in the viewpoint.

Content (please ensure you mask any confidential information):

We have a text extract, comma delimited, using quotes for text values. We have a string property that is inherited positionally. For just four out of thousands of records in the extract this property shows as blank while the values for these four look correct in the viewpoint. They show that the value is inherited. Their siblings have the right values in the extract. I thought to clear the value just in case it had been overridden, but the Clear menu option is not selectable. I checked the history to see if there had