Bud's Bad Manners

Bud was such an adorable sweet love bug as a pup. He still is BUT he has been getting in trouble playing off leach at our beach. This behavior is very serious. My trainers are surprised when it happens. What Bud does is dog talk to another usually a submissive pup or old dog. He has done this about a dozen times in life. He jumps on the poor a dog with hackles up with allot of growing and noise for 1 second and he is fine they can smell is bottom or sniff him and they play. This has never happened while Bud's on duty. Dogs approached often and he remains calm. I feel so strongly that this has to stop! I need to try to understand Bud's action in order to help him stop doing this. I have known for a long time that is overly sensitive. Working dogs are not good if they are too sensitive to noise machines, people etc. Bud was socialized early. But this happened to him when he was about 6 months old with a Golden Retriever. The Golden, older jumped on Bud with the same posturing and noise and Bud came running for dear life into my arm on the beach
Well, the other day he did it again and the dog fought back. I was in shock to see my sweet Bud in a dog fight on the beach. The other dog was on leach and walking with two men. The fight lasted 2 sec. Bud came right when I called him. The dog bit his cheek. Bud thankfully never bites. So now Bud can't play around other dogs off leach until we figure this out. WHAT A MESS! The fix is going to cost money for the dog trainer, Ericka Fromm who is great and has worked with and Bud in the past. Bud is on restriction and can't until his minor bite heals. Luckily it was just broke the skin. Bud, you are giving me more gray hairs and a heart attack one of these day.
I am open to comment's or suggestions. I am now thinking about a shock collar. This is serious boniness.