It happens real fast,and til your told it would not seem to be something you would think of.
Older thread about the same question the OP had. They also talk about the danger that the 3PH has no down pressure. The trailer tongue can lift the hitch arms when backing up etc.
http://www.tractorbynet.com/forums/attachments/187160-stabilizing-cross-drawbar-trailer.html
That would do fine as far as keeping the drawbar from rotating but I am not sure how it would do as a receiver hitch. I prefer a solid square tube.