Puppy 16 weeks attacking older dog.

2 times in the last 2 days I saw it myself. The puppy attacked our other dog. He is bigger and could really hurt him. It is happening after eating only. Even if I feed them separately which I am. 2 other times I heard “scuffling” but didn’t know who started it. I truly do not think it is playing because I see him when he is playing and now I’m unfortunately very stressed and don’t want to take the puppy back but I will have to if this continues 😭😭 any advice?