"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:


The certainty of karma.
The magnification of karma.
Not experiencing the effects of actions you did not do.
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.
Same situation can have many results from many causes. 

For the example: eyes have 34 elements that are formed from 4 kinds of difference causes (kamma, consciousness, temperature, and nutrient).

Another example: pathavi-dhatu, that is arise by temperature in eyes, also depend on the other co arising elements, same time arising causes, too.