It's either:

The switch at the end of the long ramp right before the reel. That's a flaky switch.

Make sure you have the clear eom belt on the reel. Get it at Marco parts. http://www.marcospecialties.com/pinball-parts/03-8614

Clean optos under reel.

When you lock a ball in the reel does a ball eject into the shooter lane? If not it's probably the switch before the reel.

It doesn't put another ball in the shooter lane because your switch 35 isn't working. Get that switch to register and your good to go. The second a ball hits that switch it pushes another ball into shooter lane. Make sure you wired the switch correctly and that it is hooked up underneath playfield. If that switch doesn't work it won't lock you ball it will shoot it back to pf.

Hey make sure when a ball goes through the long ramp to the reel it actually hits the switch before it goes into the reel. You may need to adjust that switch so the ball activates it. When testing any switch it's important to also test it with a ball to make sure that activates it.