A couple of times I have chased after my 6 month old border collie when she has had something really bad in her mouth and now she actively looks for things to run away with, hide under the bed or just play keep away. Now it's like she's doing this intentionally and will go looking for stuff (I have caught her trying to dig out socks in the washing basket). I know this is my fault and we are still working on drop it and leave it but even in training/fetch etc she starts off listening and doing what she is told but then I suppose she gets over exited and won't drop the ball. If we stop playing she then goes to find something to pick up? Any suggestions, please?