For towing with cars I have the impression we (owners) need to know a little more on how the WDH works.
On the link below is a really nice article about the importance of ball mount angle.
Go to page 6 => RV Lifestyle - Vol. 44 No. 2
If you can not make WD work one of three things:
1 - WDH set up is not right (ball angle)?
2 - Spring bars spec. below what you need.
3 - Your hitch is twisting...
For 2 you will need stronger bars
For 3 you will need to reinforce your hitch.
What is the tongue weight of your trailer?
What pressure you load on the rear suspension bags?