Bleeding ink from heat stamp

I've seen some heat stamps messier than others, yes. The heat stamp on my Taiga pocket agenda seems more 'fuzzy' around the edges, less crisp, than those on the other pieces I own. I also had that piece hot stamped with my initials, and the first one I received was terrible - I had to return it and have a new one sent to me. Perhaps the interior of the Taiga leather is more difficult to stamp. Never noticed the colour bleeding out on any of my pieces' heat stamps, though.