Cat and dog relationship

Hello everyone, I wanted to ask for advice about our dog. He gets along well with our cats typically, and they have been living together for almost 6 years (since our cats were kittens). A few months ago I heard a noise in the hallway and went to look when one of the cats cried out. I noticed that our dog appeared to be playing with one of our cats (bent low on his front paws and dodging back and forth near the cat). It looked like the dog was trying to play with the cat the same way he plays with my parent's small dog when he visits. When our cat cried out he ran away from the dog, and the dog did not chase him. I checked on our cat and saw that he had a scratch on his face and appeared to be a little bit shaken. He quickly warmed back up after I sat with him, and soon both the cat and dog acted as if nothing had happened and were napping together like normal. They are both very close and often sleep together, and the cat has never appeared to be afraid of the dog.
Today, we noticed another scratch on the same cat's face and believe it might have been the dog again. When we noticed the scratch, the cat was coming over to lay on one of us, and he seemed okay other than the scratch. He let us look at it and has not been scratching at it or seem to be bothered by it at all. It does not appear to be swollen or infected. We reached out to our vet, and they're not concerned about the scratch.

Our main concern, and my question to you, is has anyone else ever had a situation like this where their dog and cat suddenly did not get along a few times, and should we be concerned? The other cats seem completely comfortable at home and have never had anything like this happen. Our dog is getting older, so I did not know if this is something that we need to watch out for, or be concerned about as he ages (he is 8 1/2 years old now).