thetypewriterman

I checked the capital OO check and everything is fine - they are slightly overlapping as you mentioned.
However I found out that if I hard push the carriage to the right to start typing new line, the first letter will be in good position and all new lines will have a good precise margin and first letters. So I think that the margin is good positioned mechanically, but something hardly get in the adequate place if I push the carriage gently (if I push hard at the end of the margin, everything is fine but I think that is not a good solution for a nice machine).  

Best regards

It looks like that there is a succes with the margin rack! Now it works even if I push the lever softly
Unfortunately it is a big no-no for the line-lock... As you said, the mechanism (line lock lever etc.) in the case of the typewriter works, I compared with the other SG3 that I have. 
I have tested the mechanism with the other smaller carriage that I have (it is an awful condition), and it works! The stop mechanism in the small carriage is the same as in the wide carriage. I have adjusted the stop margin "tooth" that rings the bell and after the bell it slides trough a metal plate, but nothing... Interesting problem