If you find this, you must verify/repair your aux driver tie back voltage, replace the drive transistor on the aux driver, AND replace the coil before turning the game back on; replacing/repairing any of the above without doing all 3 will result in a melted coil.

More than likely it's NOT the coil itself as the as the AE-23-800 coil has more than enough power to get the job done. Anything related to the coil itself would be limited to the sleeve or possibly having a worn or incorrect coil stop. The most likely cause of energy loss is the ball is hitting something along the way, most likely are is the point where it enters the playfield, even minor adjustments can cause a large change in the balls trajectory.