I have three Byrds, Raven2, Cara Cara 2, and a Hawkbill. The Raven and Cara were fine out-of-the-box, but the Hawkbill was super tight, and even like you mentioned, it was still stiff EVEN WITH THE PIVOT SCREW BACKED OUT! I finally figured out that the handle screw closest to the piviot screw was so tight it was pinching the lock spring. Don't know if this could happen to your Cara Cara, but it's worth checking.
Tenacious Black Blade---Resilience---Persistence---Ambitious---Cara Cara 2---Hawkbill ---Manbug ---Tenacious Full SpyderEdge---Raven 2---Robin2---Matriarch 2
I'm only using black until Spyderco comes out with something darker.