Tell it to attack? "No, I don't think I can do that." The thing to do is hold down control, and then position the SSX where the target is in the circle, and thankfully it auto-attacks. But it doesn't have the sense itself to move within range when you order it to atack.
Joking aside, I've never really had problems with it. Was it on the new PTE? If so it could be a bug with how orbital wait periods are now in.
I've noticed its kinda wonky, I got used to just telling its path to go overlap what I needed dead. Though its been somewhat more reliable since release. For me anyway.