Customers have asked in the past or may have a scenario where an Update Set was being committed and has been stopped before it has completed committing the full Update Set. If they then try and re-commit the Update Set again this should not cause an issue.
Re-importing/Re-committing an Update Set which has been committed already
If an Update Set has been committed already or was abruptly stopped while it was committing, re-committing the Update Set does not cause any issues.
However, if some records have been committed by the Update Set and then on the target instance, an update has been done on the record before re-committing the Update Set, a collision will occur when previewing the Update Set.
If for example, you have records which are being created in your Update Set, and has been committed already or has not completed committing, when re-committing again this will not create duplicate records. In fact, when committing, the instance will notice that the records have already been created/updated and will skip these updates within the Update Set.
This scenario may occur if Update Set has been cancelled whilst committing (which should be a rare case and is not recommended to be done).