Valve seals tore on break in

It could be something else but whenever I have seen this it was from the retainer contacting the seal. One time I saw a seal that didn't get installed correctly (all the way down on the guide) which then caused the retainer to contact the seal and chew it up. I would check the retainer to guide clearance before you tear it apart. If you haven't removed the seals that are damaged inspect the to see that they were installed properly ( all the way down).