Crown wheel of course.... screw has no shoulder probably the washer was then lost.
I am learning... very slowly... went to bed 4:15 this morning. I was shocked by the result after the cleaning i guess i must pay the price of the knowledge. Very painful so far and not much knowledge gained, well to my former myself i go with lightspeed but it is just not enough and they say there is no 2 x lightspeed.
1-Imperfect hairspring coil can foul itself when amplitude gets too high so the rate goes fast , until such time that HS coil jumps back to normal.
2- Loose and pushed back guard pin, fails to guard the roller table- impulse jewel properly, in which case if the balance wheel gets in a hurry on wrist it is susceptible to the condition in section 1.
Faulty guarding by the pin, can let the condition for sticking to come about.
What you have circled in the picture is the crown wheel and screw. The screw should have a shoulder section to keep it distanced, or a (lost) washer was used there.
That is why I wash with petroleum only and IPA only, by hand. And mild ammonia only if there are brass / gilted parts.
Then every other thread we read about beginners (but not only) getting fixated on on machines and commercial solutions.
Unfortunately not, i was thinking of that, but the ratchet wheel has a recess so the screw could center it and the wheel should be able to turn around it. Now that I see the picture it is actually upside down but it is just because i put it back for the picture and did not pay attention.