It doesn't seem like all features are being selected for some reason. Can you try it in ordered?
Always a good idea to upload the file here. Especially when it's such a small one.
You can see in Your video that even although t
You do a box select and all surfaces are shown green, the two base features (cylindars) in the pathfinder are not shown as selected.
Select them too and the mirror will work
OK, the problem is the thread feature. For some reason when that's picked, like with a window selection, the thread can't be mirrored but it also leaves out the protrusion on which the thread is based. You should have gotten an error pop-up. So just pick everything except the thread in the pathfinder. But it seems you can't apply another thread to that new cylinder for some reason.
Also you can't mirror sync features in ordered but you can do "mirror copy part" which does take the thread.
That might work for you too.
edit: I see you discoverd the mirror copy part.