Fractures like that are more due to metal impact or sever temperature changes. Those are sharp edges in a smothe bore. That means something hit them or excessive force was applied very quickly.
Since the rods look like new, there are a few things you may want to look at:
1. If these are adustable or hydraulic lifter, where are the rest of the parts and what do they look like?
2. You may have recieved a bad set of lifters from the manufacturer. It would be the first time.
3. Are the guide out of alignment? Stupid as this might sound, they could walk out of the pocket.
4. How old was the assembly lub on the bump stick before youstarted it? If it was put in a long time ago, there may have been only the shightest coating.
5. I am not familiar with your setup, but it that a small block ford, Cleveland by any chance? If it is, did you have the galley mods done? The
oil rail some people put down the center comes apart if not installed correctly and the lifter bores immediately starve causing them to freeze up.
6. It look like the side of the lifter was hit. how are the valves and pistons?
Hey I hope this helps and please let us know what you find. This looks way to strange for bind in springs or piston to valve problems. Looks like you got yourself a set of lifters made in Iraq.
Just bit of humor to lighten this. Sorry for your troubles.