if you read the technical document found above you'll notice on page 3 there is reference to another document? This is the document you need which explains how to fix the problem of the new weight becoming stuck if it's not properly adjusted. The only problem is you're not going to have the tools. But in the absence of lacking of the proper tools I'm extracting out the text that you will find interesting
"The new oscillating weight becomes stuck if it is not adjusted to the stud (pin). The new studs designed for the oscillating weight in the calibre 550 family are 0.698 to 0.701 mm in diameter."
The reamer is described as "Hard metal precision reamer Diameter 0,702 mm Reference 516 0072" then even if you can find the reamer you need the spindle that holds it in the staking set. So what we get out of this is the axle is over size and you need to open the hole to 0,702 mm. I would suggest not using the old parts just replace both of them. then if you're careful you can use watchweasol instructions with a brooch which will work just be careful it's easy to go too far.
Thanks guys, I've done a few watches, and I hardly ever break them now . I've been enjoying servicing old Russian watches, cheap and cheerful. But I was curious to see how different clocks are. I just took a look on the bay at Smith's they look great. There's one listed close to me (so cheap postage) and only $aud20. It's listed as a mantle but the winding key is at the back not on the face?