I just finished solving a similar problem.
There can be several issues at work.
What I did:
I first removed the apron - exposing the entire works. This area gets filthy and I guarantee it's in need of a cleaning.
Next, I removed the ramp and ball guide assembly - everything cleaned and polished with cleaner ( I just use the Novus 2).
At the end of the "v" shaped ramp - just before it serves the ball to the shooter lane - there will be a curved kickout lever (from beneath the playfield). Check the "true-ness" of this piece of metal. The curved, flat, kickout actuator arm can become deformed and conflict with the switch extension lever located right next to it.
While you're in there, check the alignment of the auto-fire kicker, shooter lane diverter gate assembly, and (carefully, gently) re-torque all of the screws you can get a wrench on. If anything is stripped, use the tooth-pick/glue trick to re-fill the hole and start again fresh.
When were your coil assemblies last rebuilt?
Consider at least replacing the coil sleeves for everything under the apron and polishing the pistons.