beat a dead horse vs sort out

beat a dead horse

verb
  • To persist or continue far beyond any purpose, interest or reason. 

sort out

verb
  • To provide (somebody) with a necessity, or a solution to a problem. 

  • To fix, as a problem. 

  • To separate from the remainder of a group; often construed with from. 

  • To clarify by reviewing mentally. 

  • To arrange. 

  • To organise or separate into groups, as a collection of items, so as to make tidy. 

  • To attack physically. 

How often have the words beat a dead horse and sort out occurred in a corpus of books? (source: Google Ngram Viewer )