I bought a Pioneer brand freeze plug set on a 340 I am doing, having had success with them years ago. Somewhere along the line they shortened the wall height on them to save a whole penny on the set. They don't have enough support and want to cock in the bore. Garbage.
I chucked them and went with Sealed Power which has the taller original wall heights. They sit square in the bore and are tight.
Also a member here gave good advice to install them by driving them in against the top of the wall edge and not insert/drive a socket against the bottom of the cup.