You ever strip all the tape off and flex the handle by the head to really check the grain? That's how I caught one on a sledge last year, same deal, hairline split hidden under the grip tape. I don't replace handles anymore, I just buy a new tool and swap the head onto a fresh hickory handle if it's worth saving. For a cross peen, a new handle is like 10 bucks and 20 minutes of work with a rasp and some epoxy. Way cheaper than a new hammer, and you know the grain is solid once you hang it right.

...and that's exactly the kind of thing you only pick up from somebody who's been doing it for forty years. I had a guy in Texas once show me a trick with a curved boning knife that let me get the belly off cleaner, but I never could make it work as smooth as he did. It's funny how those little shortcuts stick with you though, even when you can't quite replicate them yourself.