I think everyone has given you some good things to think about and research, so I won't add too much

I think you said the first time in Dayton, he started to "have issues" immediately. But what about the most recent time, with the water dish?

Reason I ask, was just a thought I had. In Findlay, there didn't seem to be any problems until later in the afternoon. Is it possible, Bon getting tired is a contributing factor? Not to say that is only only thing going on, but maybe for a while shorter trips to the park would help? Or let him play a bit, then remove him from the park, for a quick snooze, and let him back at it? I know at dayschool they have the puppies take more naps, then the older dogs, and it seems to help.

I think you and Mark both have done a great job with Bon. You started training him early, and have socialized him early. I hope this is just a bump in the road, as he goes through those "teenage" years. As Staci said, we'd sure miss Bon if he couldn't come to the park anymore!!