not all lurchers will take squartter's, alot like your dog looks for movment in the beam. When you get your next squatter, walk your dog up to it, get your dog to the back of the rabbit, when the rabbit gets up slip your dog. It should learn take them , give it time. How old is your dog, it takes a couple of seasons to know the crack.
I concur with bird on this point. If you can help the dog on ther angle of aproach it can sometimes omit the need to turn in the 1st stride or 2. . . . . if you know what I mean . . . . well I know what I mean ant way