auch ein blindes Huhn findet mal ein Korn

Etymology
lit. 'even a blind hen/chicken finds a grain at times'.

Proverb

 * 1) success depends in part on coincidence; every dog has its day, even a blind squirrel can find a nut once in a while
 * 2)  even someone less capable or less gifted may at some point be successful
 * 3)  someone’s being successful in, or right about, a particular matter need not mean that they are capable