Ok. First post:
Who has been in a plateau? I watch dollars disappear as accuracy fades. I am paying an operator to disappoint myself.
When someone has found a breakthrough, and a good long run of mediocre scores suddenly gives way to consistent improvement, was there a specific choice that caused it to happen? A change of focus or gameplay? Or do the Pinball gods just listen to our cursing?
I don’t think we’ve ever played a match together, so I don’t know your style of play, but here’s some general tips I give people: no one is as accurate as you want to be, so a lot of pushing past a plateau involves
a) improving your consistency.
b) improving your chance of recovery when you miss.
Improving your consistency: try playing with more control. Play with other people who are better than you or watch video of people better than you, specifically at dead bouncing, drop catching, live catching, etc. Anything that slows the ball down, and provides you more shots coming from a consistent stopped (cradled) position. During multiball, have you tried playing cradle/controlled multiball instead of flail-away multiball?
(B) Are you nudging enough and at the right times? Same comment as above regarding playing/watching people better than you. Are you choosing strategies and shots that provide good reward with the least amount of risk?
I know you said your dollars are disappearing but, my advice would be to not concentrate on scores or outcomes. Try to analyze your play and play with the goal of improving your technique instead of your score. If you aren’t sure if your technique needs improving watch all the videos that @Snailman mentioned.
I would also suggest playing one game with skill building in mind only and other games for fun/score. By playing the same game over and over you get to see the same bounces and the result of the bounces more times. If there is a shot, bounce, feed etc, that causes drains you will get more opportunities to first notice its happening and learn how to make adjustments to deal with it.
I have hit plateaus and I had to really pay more attention to everything that I was doing. I also changed my play style up a bit. When I started playing I played purely control. One of Bowen’s tutorials mentioned trying to make your shots from a cradle and thats exactly what I tried to do no matter how many times it cost me a ball/game. Later, I came across games that I just couldn’t control and usually the result would be disastrous. I started playing strictly on the fly and came up with a game that would help me develop my on the fly play. Now I have a hard time not playing on the fly because its just fun!
If you haven’t already, you should read this thread. Looking to get better- what might I be missing?
Another interesting thing I noticed was playing on location in league after attending papa this year. All the balls seemed to move it slow motion. I felt unstoppable. I attribute it to playing hard games. Like warming up with weights on your bat. Of course it also could have to do with doing nothing but playing Pinball for several days straight. Or maybe the key to Pinball is waiting in lines 
+1 to everything in that thread- I can attest that it did, in fact, make me better!