A 5th wheel just doesn't react as quickly as a trailer because of the hitch location. Sometimes there just isn't room to maneuver the truck even though the spot is plenty big enough for your rig. Like Showme 5vr, I have disconnected in order to straighten the truck and finish the job. The spot I am currently in as a matter of fact, because there is a honkin great palm tree in the way and the road is too narrow to pull the truck far enough forward to straighten it up.
On the other hand, after spending time with my 5th wheel, I have a heck of a time backing up my 12' utility trailer until I get used to it again.