Nice shape and proportions. What you describe is the perfect action for this kind of bait, you have managed to get the maximum action out of the bait. This is confirmed by the 180 turn on the pause. This is caused by the last vortex acting on the bait.
In my opinion, the roll is caused by the joint being too tight. It is a very tidy joint, but if the joint touches during the swim, the joint will freeze and the force from the vortex will push the bait over (roll).
Correct, deep swimmers create such large vortex turbulence, that prevents the glide. Gliders, which are beyond my personal experience, are generally one piece and torpedo shaped. They use the same water forces, but the shape greatly reduces the force. Apply a twitch and the vortex sets the direction of the bait. The bait then glides beyond the effects of the vortex. The next twitch always reverses the direction.
If you want to stay with the two piece, you will have to reduce the efficiency of the swim. Increasing the front length ratio to 2:1. A lot of trial and error work ahead. Another thing to play with is the nose position. Yours is currently central, try a high or a low nose. A more rounded forehead section will help too.
Dave