I have had exactly the same problem with my chain since we bought the boat.
I have the ISO chain with 30mm inside dimension and the WASI powerball, now fitted to my gal Rocna. (Yes, I now have a different dissimilar metals problem than before :-)
I’ve reached the conclusion that it’s just another feature of the boat. I tend to lay shorter chain with the Rocna, so the problem happens less frequently for me.
See you in Preveza soon.
Sent from my iPhone X