Unfortunately we still haven't gotten to the bottom of what's going on with Benny. We've had to add gabapentin to the metacam as the metacam alone was no longer working. Thankfully he's eating, moving, and happy again. I recently took him for further xrays, a physical, and a blood test. A radiologist said there are some possible changes in the muscles of his hind legs, but otherwise there's nothing unusual. My vet is going to follow up with them about that to see if that might be a new lead. Everything else remains normal. No arthritis, no issues with his heart, kidney, liver, etc. I've also learned that the stones in his salivary glands might not actually be in his salivary glands. They aren't able to tell where exactly they are, but because they're in the location of the salivary glands, they assume they're salivary stones.