The breaker cam (that little lumpy lobe that opens the points) wears down asymmetrically. This causes "point bounce" at high RPM.
The Scintilla Magneto Manual refers to several editions of service and overhaul handbooks (often published by Scintilla AG, later part of Bosch) covering aircraft, industrial, and high-performance magneto ignitions. Common manual numbers include M-2030 , M-2055 , or military variants like AN 01-35DC-2 . These are not casual reading — they are dense, line-art-heavy repair manuals for mechanics working on engines from the 1930s–1970s. scintilla magneto manual
If you are restoring or maintaining a Scintilla magneto, these are the standard manual procedures. The breaker cam (that little lumpy lobe that