i just received a few SSK's from Cindy, kind of quick from America to Germany.

Just a quick question, after how many broken rivets you should do a bolt-mod?...
There are three SSK's, one has 9 broken rivets, another one 11 + a damaged spring, and the last one 7 + 1 spring felt off from the hammer.
On all of them a few keys doesn't clicked, a few stucked when pressed down and from one ESC key the spring is damaged.
I could steal some springs/hammers from my full-size Model M, which would then also need a bolt-mod and two springs to work again...
Any advices?

Best regards,
David