I had a water hammer issue in my house as well. I try purging the water system to get the air out, I tried installing water hammer arrestors, and I also tried strapping down some pipes. Nothing worked.
Then one day my water heater went on me so I had it replaced. Since then I have no water hammer issues at all. Doesn't make sense to me but this may the same case for you?
Then one day my water heater went on me so I had it replaced. Since then I have no water hammer issues at all. Doesn't make sense to me but this may the same case for you?