I suspect one or both double spring mechanism (unit), which straddles the rocker surfaces on each side, is positioned incorrectly OR... The rocker surfaces do not have the correct arc to one or both OR.... The guage of the springs are not appropriate for that particular chair.
What exactly is the rocker action doing wrong? 1) uneven rocking action, 2) rocks too far forward, 3) rocks too far back, 4) rocks too far forward and back?
Did the double spring units come with the/a kit or did you purchase the double spring units separately? There are different guages of wire/spring used on platform rockers, recliner rockers, etc..... Depends on the chair, as to what guage of spring is appropriate for the particular chair. Did the plans recommend a particular guage of spring units to be used?
Sonny