Without knowing it most people telegraph their motions.
It could be something very subtle but the dogs still notice so it's careful not to be sloppy. For example you may have a dog that seemingly is not taking your casts properly but is actually moving early as soon as you move your foot but before your hand is actually extended so he never sees the actual cast.
So, stand still, hold both hands in the prayer position palms together close to your chest , feet slightly apart and whistle in your mouth. Go to work from there. Hand and forearm will normally be the first thing to move and preferably cast slowly without that quick stab the sky motion.
It could be something very subtle but the dogs still notice so it's careful not to be sloppy. For example you may have a dog that seemingly is not taking your casts properly but is actually moving early as soon as you move your foot but before your hand is actually extended so he never sees the actual cast.
So, stand still, hold both hands in the prayer position palms together close to your chest , feet slightly apart and whistle in your mouth. Go to work from there. Hand and forearm will normally be the first thing to move and preferably cast slowly without that quick stab the sky motion.