Kenmore 1946 - Buttonhole function STILL broken! Help?

Good morning, and happy Friday everyone!!

Since this week has been almost entirely about sewing machines, I may as well just finish the week off the same way, right?

One of the machines I'm working on is this Kenmore Model 1946. This is also my favorite outtake from this week:

I first showed her to you here.  She's actually an interesting machine - she does a straight stitch with a built in metal camstack.  That means I don't have to insert cams to change stitches like I need to in my other Kenmore.  In addition, the metal cams are more durable than nylon/plastic ones that show up in later models of many brands.

This is also an early version of the free arm - the metal "C" around the left of the base detaches for free arm sewing - you'd use this for things such as sleeves, pant legs, and so forth. Small circular bits of fabric - it just makes them more manageable, but you don't have to have it.

I spent many hours tuning her up, cleaning her out, and oiling all the bits and pieces as directed. The feed dogs wouldn't lower for the longest time.  Feed dogs move your fabric along as you sew, and if you do a buttonhole using a function on the machine, they also move your fabric in the right configuration to make the shape.  Some people also do something called Free Motion Quilting (FMQ) where you need to drop the feed dogs entirely to quilt. 

Anyway, after lots of playing, tweaking, cleaning, oiling, etc, they now move freely.  Which is fabulous.  

There is one issue left, and I can't figure out for the life of me. Maybe you know about this machine, or just have a fresh eye. Here's the setup. 

This machine does a buttonhole using a buttonhole foot and you manipulate it using a knob to turn directions. When I first got the machine, the knob was entirely jammed. Now, it moves freely - too freely.  

When you take off the handwheel and the side plate of the machine, this is what you see:

See where my finger is? It's actually pushing down the bit that gets stuck in the highest position.  Let me go back for a second: what you are looking at is the side of the machine.  The top metal knob is where the handwheel (the part you can turn from the outside) is located. There's a drive belt that attaches to this, and runs to the other metal knob with the motor belt on it.  Hence, the motor turns, moves the belt, the bottom wheel turns, moves the other belt, the handwheel turns, the machine sews. Got it?  The power switch is just between my forefinger and my thumb. The machine is definitely unplugged as I work on it.

Anyway, the part where my finger is gets stuck in the highest position - there are three positions - the orange dot, F, and R on the dial. It's the top knob.

I can move the part back to here by pushing it with my forefinger.  Not so convenient when you are making a buttonhole.

I have oiled, cleaned, WD-40'd it, and everything. Nothing appears bent.  So I think I'm possibly missing a spring.  In this next photo, there's a long spring in the middle of the photo. Just behind and to the right of it, is a little dark metal piece with a hole in it. I THINK I need a spring in this part to pull the setup back down, but I'm not sure where it would attach.

If you go to the Sears Parts Direct Site, you can enter in your model number and it will pull up a list of parts and some blown up parts diagrams. Here's the diagrams for my model.  I can't seem to figure the issue out from those diagrams, as the quality is a bit fuzzy. But I am thrilled to have access to them - it has definitely helped!

I'm completely stumped by this issue - the machine is a solid metal workhorse, and every other function on it is flawless.  It even has a case!

It's a machine I hoped to pass onto someone, but I can't do it if I can't get this working. Does anyone have any tips or ideas?

If your eyes have completely glazed over by now, here's a cute picture, completely unrelated - Caught Mr. C "reading" an Interweave Knits ad. Sweet. :)

Mr. Tupelo and Mr A are going hunting this weekend, so it's just me and the little man. Here's hoping it's a great weekend, and for you to!

Jess