I mirrored a susp chassis I've been working on, and it duplicated it like 30 times and moved it somewhere else, and the parts are all over the place. It's best to just build the other side of your project yourself. The mirror feature is just a murderer with builds. Or it's definition of a mirror is "first say there's already a part there, then duplicate 30 times when he didn't ask for it, twirl it make it crooked, he wants the suspension 500 feet away, that tire can be the first cloning project, 30 beacons because he needs to see what he's doing. Oops, almost forgot that he spent 50 minutes on both suspension mechanisms! Better space out those hinges and have them scattered 70 feet from eachother! All done!" I undo what the undo feature does: "okay we need to move the chassis off of his screen! Done! It's off!" I undo again "OOH! Better keep the mirror damage! I think I'll just go back to one of his other builds!" Facedesk

if you want to mirror something, do it yourself. If you wanna undo something, do it yourself, or you'll end up with a build that looked like it exploded.