The drop targets falling when they shouldn't might be due to the solenoid expander board under the left side of the playfield. There's a lamp right next to it that's part of the solenoid expander activation circuit. Put the game in lamp test mode. If that lamp isn't flashing, replace it. Otherwise remove the solenoid expander board and reflow any bad solder joints you see.

From memory, switch 41 is a single switch in the middle of the zipper flippers and comes up closed in the switch test when the zipper flippers are wide open. Lift the playfield and manually activate the coil that pulls in the zipper flippers and see if #41 stops blinking in switch test mode.
The Bally switch test mode only shows you the lowest number switch that's closed. So if all switches 41 through to 48 are closed, the switch test will only report switch #41. Coincidentally the seven upper drop targets are switches 42-48 so until you open switch 41, you won't see the drop targets switches in the switch test.

Oh yes looking at the schematic, I see what you mean. It will be the diodes on the coils you see with one leg connected to either a brown/orange wire or a grey/red wire that might be shorted.

Well done

These Bally flipper cranks look pretty close to me:

http://www.marcospecialties.com/pinball-parts/A-1889-7
http://www.marcospecialties.com/pinball-parts/A-1889-8

The cranks on my zipper flippers are horribly worn because of metal to metal wear at the plunger pivot. I haven't investigated it yet but I'd like to see if any traditional crank and plunger rod with link from that era can be used instead.

Sir, I also recently got a Medusa and have the EXACT SAME PROBLEM! I've been driving myself crazy by checking everything I'm supposed to check, to no avail. I'm going to run down to my basement now and check if by chance the knocker coil is in the same mis-wire situation. But that would be really weird to have the same mis-wiring. I will report back. I also just ordered a brand new solenoid expander board as you did. Thought it was worth the $40 because this board does seem to control the coils I'm struggling with and my original board had some very sloppy looking reflow work done on it, with a missing plastic cover and looks slightly toasty. In addition to my 7 bank drops not resetting properly, I also get the 41 EOS switch error. Also when either of the drop target assemblies reset, for some reason the ball launch coil also erroneously fires. And when it fires to launch a ball, it seems to be under powered and does not have enough kick to get the ball out of the trough even though the coil and sleeve assembly are good. Also the saucer coil does not kick out the ball even though the switch is working. Basically all the coils on this circuit are not working as they should. It's all got to be related to something similar as on your machine.

I have so far checked the U10 and U11 IC's that drive the switch matrix and coils on the MPU, had the Solenoid Driver Board professionally serviced along with the S&T board and put in a fresh lamp matrix board, reflowed headers, visually inspected for any shorted, twisted, or broken diodes or caps under the playfield, meter checked all the associated switch diodes, checked the solenoid expander light bulb, etc. Still the same problem. : (

Got my problem solved with the help of Toyguy and Pinwiki. Basically one simple problem apparently caused the previous owner fix the wrong thing and create a new series of problems. It went like this:

1. saucer switch was apparently a littlle bent out of shape, therefore the saucer did not work.
2. the guy deduced it was a faulty coil, so he replaced it with a completely incorrect coil. Instead of being a Bally 3 lug, 2 diode coil, he put in a Williams 2 lug, 1 diode coil. This sent crosstalk voltage to other coils in the same circuit.
3. The coils in this circuit are on the solenoid expander board. This board looked like it had been worked on several times before, meaning someone already had doubts about it.
4. When I clipped off the incorrect saucer coil and booted the machine, the expander board made a loud buzzing noise as if it's relay was not working correctly.

So my solution was to install the correct, 3 lug, 2 doide Bally saucer coil AND to replace the buzzing, hacked solenoid expander board with a new one. $55 later, everything works perfectly. Did not have to go through the machine and check / replace every diode, thank God.

My learning experience from this is on Medusa, you have all the drop target coils, the knocker, the ball launcher, and the saucer coil all on the solenoid expander board. This in turn actually runs from an SCR on the lamp driver board instead of the usual solenoid driver board. If any one of these coils is malfunctioning due to a bad diode or short, or if the little Solenoid expander board is not working (with its little light bulb) then multiple problems can show up including incorrect resetting of the drop targets and failure of the ball to launch.

Shesh! All starting because a saucer switch was not adjusted correctly, per point 1. as stated above!! (incorrect saucer coil pictured below)

Photo Feb 25, 6 59 03 PM (resized).jpg

Okay, problem finally solved. After trying everything, I eventually hired a professional pinball repair guy who solved the problem in about an hour. So in summary: Auxiliary coil circuit with the drop target coils, knocker, saucer, and ball launch were acting flaky or not working intermittently....

- pulled every coil and checked it
- replaced every diode on every coil in this circuit of coils, even though they all tested good
- replaced the auxiliary coil driver board with a brand new one
- replaced the lamp driver board with a new one (it drives the aux coil board)
- also replaced the auxiliary lamp driver board while I was at it
- replaced the the entire MPU board with a new one
- replaced the rectifier board with a new one - it was a little toasty anyhow
- sent out the power driver board and sound board out for professional testing and refurb

Problem still remained. And the final culprit... a poorly repinned molex connector on the J4 connector of the power driver board! There were two little wires shorted and almost touching, looking even a little burned. Also reflowed the header for J4.

Well, I learned a lot and now I have all these great new parts in my machine! But I spent hundreds of dollars and wasted weeks of time trying to figure this out. I am posting this on the Medusa forum so hopefully someone else can solve their problems quicker than me!

IMG_1243 (resized).JPG

Yikes, maybe clip your coil wires closer to the lug next time. You're gonna run out of harness.