to mean it seems like you're teaching him "ok" means come. after you say
"ok" and he comes to you why don't you praise him for coming then say "down".
leash him, take a few steps and stop then say "down". you can do circles,
figure 8's, serpentines, back up, "stop", "ok (come)" and include "down" as
part of the exercise. you give a harsh "down". why don't you give him the
"down" in that happy voice?