At the request of brink and com I decided to post this.
I noticed today that the sera acu has a minimum range of 2 while the other acus have a minimum range of 1, this seemed very odd, so I tested it and it seems that even though the other acus can attempt to target the unit between 1-2 range it cannot fully target it, instead moving back and forth, a twitching motion which we sometimes see when an acu tries to build something really close to it. I'm just interested maybe we can just increase minimum range for other acus or possibly decrease by 1 for sera. All of this was tested with aeon scout so the twitching may be a result of the height of the scout, but i haven't really tested much because this is purely for archiving purposes until next balance patch occurs.