Fast lane

Maybe it is because the solenoid that drops the starting pins is on that side of the track, which causes a slight deflection on that side due to the force of the solenoid, which ends up dropping that pin a little ahead of the others.

Maybe if the solenoid were in the center it would eliminate this issue?

Just the first thing that came to mind for me.
 
Are you using a spring on each side of the gate? Maybe move the springs around to different locations on the gate. Or a spring might be stretched. Do you un hook them between sessions?