There was a cir clip problem about 2 years back I think that was gudgeon pin related.
The piston is based on the old V6 Holden engine piston and is manufactured at the same factory where ACL makes all their pistons. There are a few machining differences, the cir clip grooves, and a wider ring groove.
Stanwell…….I really can't answer your question I am not involved enough, just have a lot of exposure through various avenues.