This is happened due to programmer mistake.As per tool path generation guidelines,which tool they select to generate tool path program name should be same for that tool.In this case what happened is programmer generated with dia 12f endmill ie,inside the program name is 30_007_0214_12F & given for dia 16f endmill ie, out side program name is 30_007_0214_16F.So operator seen at out side program name & selected 16F,runned the program.