WD Hitch, Still a large amount of sway occasionally... help

With the trailer weighing 4000# the tongue weight should be ideally 13% for best towing experience. Be removing 250# from the tongue weight that you stated was 550# leaving 300# or 7.5% increased the probability of severe sway, possibly more that the E-2 WDH can overcome.

The WDH that you purchased is much bigger than you need for the trailer that you have.

Here is the E2 installation Manual. It states that the tongue weight should be no less than 10% and no other sway control devise is necessary.