"Not experiencing the effects of actions you did not do" as a characteristic of karma

Referring to the Four Characteristics of Karma (catvāri karmasvabhāva), as taught in Tibetan schools: 1. The certainty of karma. 2. The magnification of karma. 3. Not experiencing the effects of actions you did not do. 4. The actions you have done do not perish. (From "The Great Treatise on the Stages of the Path to Enlightenment, Tib. Lam rim chen mo, Volume 1: Volume One" by Tsong-Kha-Pa.) I have no issue with 3 of the 4 characteristics of Karma, but it seems to me that #3 Not experiencing the effects of actions you did not do has been incorrectly extended by many to nothing can be experienced unless you have created the cause. The problem with this is that there must be some random events mixed in with cause and effect.