Difference between the column's tShipUnitGid and shipUnitGid for the SShipUnit table?

Summary:

We have encountered an issue in our ActualShipment integration, and I have read in the logs that a ship unit is being removed from the tShipUnitGid but added to the shipUnitgid columns for the SShipUnit table.

Content (please ensure you mask any confidential information):

We are having an issue with our ship units getting removed from the stop and the stop type getting flipped to an O instead of D (due to the missing ship units) on our ActualShipment integration. The issue is sporadic, and I have not succeeded in replicating using the same integration files in a lower level environment.