Question on a Hurst Roll Control unit I have installed on my Dakota.

The unit is installed in the front brake line just after the combination valve. Per the instructions this seems like the correct location. (see picture)

When I set the brake, then press the button, and release the brake pedal, the truck will only hold position for about 3 seconds before starting to creep forward at idle.

It absolutely won't hold position if I add any throttle to the equation.

Do I have a bad plunger in the roll control unit, or is something else going on?

A little extra information, the unit was originally installed incorrectly just off the master cylinder, before the combination valve, in the front brake line and did the same thing, with the only difference being it would trigger the BRAKE warning light. So this was corrected, and the combination valve was reset.

The front brakes work just fine and will hold the truck under power if I two foot the pedals. But I really would like to be able to set the roll control, do a burnout, then be able to line up and stage under throttle without rolling away.