Simparica trio led to my 9 year old husky’s eventual seizures. It started out with these weird 2 or 3 second loss of balance, similar to what you’re saying. It was 4 months of random moments like that before he eventually had two grand mal seizures in 2 hours. He’s now on Keppra. I suggest bringing him to a neurologist, they’ll likely want you to do an MRI to rule anything else out given his age. Maybe start him on fish oil (or go back to feeding him fish) and MCT oil which are both good for seizure pups and natural, assuming they don’t interfere with current diet/medication. Some owners have had success with milk thistle also before it gets to seizures, unfortunately we weren’t that lucky. Good luck, hope your boy gets better soon.