I can't answer your specific question, but I can chime in to say that when I
was training in a Seneca, I had a terrible time avoiding slamming the nose
wheel down on virtually every landing. I've never flown an airplane that
was so hard on the nose gear. Unless you carried a great deal of extra
speed into the landing, and immediately lowered the nose after touchdown, it
would slam down VERY hard during the rollout as you tried to hold it off.

Given the kind of abuse the nose gear likely takes, I would strongly suspect
long-term wear/tear and fatigue, rather than mis-rigging. But I have no
specific knowledge of how the Seneca nose gear works.

- Mark