Could the fault be the relay? Yes
Or something else? Yes
Could be the switch itself.
I had this fault on a VW Golf - the wiper motor bolts had vibrated lose and the motor was wobbling - eventually the linkage would jamb up and the wipers stop - then - when I switched off - the tension in the linkage would relax and it would all start going again when I switched on.
Eventually it all stopped working completely.
Check out the linkage...
March 2015