I noticed 2 things about rebuilding dead structures with those commands. Not sure if those issues are known or not.
Repair Command:
When you use the Repair Command with multiple engineers to rebuild a destroyed building only one of the engis actually rebuilds it while the rest does not.
Support Command:
When you have engineers/ACUS supporting a building and it dies they do not rebuild it at all. Yet SACUS can do so.
made a sandbox showing those issues.