The following are some scenarios and suggested resolutions.
1)The promotion package in in Executed status. You delete backout members in error. You require the backout members to package ship.
-regenerate the Elements and then promote them to the final stage.
2)The promotion package is in Exec-failed status.
-The best course of action is to continue with the execution of the existing package. If this is not possible copy the package and in the copied package remove the elements that have executed successfully. Then run the copied package with your changes and abandon the exec-failed package.