It looks like you have about 80 to 100 pounds hanging out the back. (I'm sort of a bike know it all!!) Most carries of this type have a bit of slop in the area where the hitch fits into the female portion. This small movement compounds to a fairly large amount of movement at the bike. The bikes can get beat up some.
If you have a bit of sway because of the weight--lose the rack! Possibly carry the smaller bikes inside the trailer. Or maybe place a couple bikes on the front of the tow unit.
At times, we have some pretty expensive bikes and carry them in the camper shell, out of sight (tinted windows), locked, and relocked.
See ya out there