There's your problem. The slop introduces movement allowing squeal.
So that's what I've "heard"
, but what I don't get is that on both my old Swift and my current one, the V-brakes (both Tektro and Avid SD5) had a lot of play in them. 2 sets of brake posts and 2 sets of V-brakes: all sloppy. I wonder why the canti brake arms fit nice and snug.