+1 to everything LOTR_breath mentioned. The first time I got two balls stuck on the magnet I waited for the ball search to clear it - don't do that. A few minutes later I was waiting for the soldering iron to heat so I could replace that transistor!
I had the same problem with bounce outs and a few other things could be causing it. Check that the spinner at the ramp entrance is hanging at 90 degrees to the playfield, which means the top edge is slightly tilted towards the player. It tends to mushroom over time and hang with the bottom edge towards the player, which can rob the ball of momentum as it enters. Carefully bending the wire arms will change the angle at which it hangs.
The tips of the ring ramp will also mushroom from rejected ring shots, and can affect the ball if it gets too bad. File those down flat.
You can also slightly adjust the aim of the ramp by loosening the mounting screws and twisting the ramp, then cranking the nuts down tightly.