Answer:

mismates

Answer	Crossword Clue
MISMATES	Arranges in the wrong pairs.
MISMATES	Matches wrongly.
MISMATES	Joins unsuitable things.

MISMATES	Slips up, as a dating service
MISMATES	Pairs socks incorrectly

Crossword

a puzzle consisting of a grid of squares and blanks into which words crossing vertically and horizontally are written according to clues.