I believe the jitter that you see in POTC (and NH too) is due to the differences in Ship_UpdateParameters() from the script files. It may have been handled differently in the old Storm 2.0 engine, but I don't know that. Anyway, I am reluctant to change the scripts for POTC because it might change the other sailing behavior too much from the original. But there is no jitter problem in COAS or CT, so it is not a bug in the engine so much as there are details in the older POTC scripts that are probably handled slightly differently by the newer engine. I could change them, but then someone else might complain that ship speeds/turning and handling is all wrong and not like the original, so I'm caught in a difficult situation; my decision was to leave the scripts alone.