Timing problems with TXPK 3.1.0.1

If I pick FixedTimeStep, it seems the parallaxing or camera movement becomes somewhat jerky on the PC. You can see this for yourself by building a PlatformerKit Starter game, then watching the waves on the ocean sprite while moving the character. Seems jerky and "double-vision" like. If you pick Interpolated instead of FixedTimeStep, the camera/parallax issue is solved (smooth), but the player input becomes really really laggy every fifteen seconds or so. Is this an issue with the PSK, or TorqueX in general? Anybody else found a solution or a workaround?