Let me start by giving a little background. Stanley is about 16 months old now. We've had him since he was 2 months old. He's been very well socialized having gone through two group training classes, monthly visits to a dog daycare and frequent trips to the dog parks. Throughout this time, Stanley's been great at the dog park. He's always been playful and confident and mixes it up with dogs of all sizes. However, in the last few weeks, his behavior at the dog park has not been the greatest. His first annoying behavior is what I guess is herding instincts kicking in. He chases after dogs barking the whole time or he'll bark at dogs that are playing together. For the first 13 months or so, he NEVER barked at the dog park. So I find this new behavior surprising and a bit annoying. However, it doesn't concern me too much as long as the other dogs and dog owners are ok with it. But the other behavior I've noticed is the growling and snarling that tends to escalate out of nowhere when he plays with some dogs. He'll be playing and wrestling just fine but then he'll start to get more vocal with grumbles and growls and his lips curl up to show his teeth and the play gets too rough for my liking. At this point, we usually pull him away from the other dog and leash him up for a time out. As a first time dog owner, I'm not as familiar with dog interactions as some and it's hard for me to gauge if this is normal play or if it's escalating to a bad place. What's the best way to determine if the play is too aggressive and what's the best way to correct the behavior? I'll probably consult the dog trainer but was looking for advice from the Corgi community :)