Valve seals tore on break in

Well they had to have been machined for those seals to fit. Sometimes when those seals are installed they can get crooked on the guide, which I can take a guess someone could have used a socket to correct that & it pinched the top.
2.
Other thing is guide height and possible keeper contact but by the looks of the photos I'd guess a variation of the 1st part.

I always take a file to the stem directly above keeper grooves because usually there's burrs or something, that gets filed down smooth again
(don't remove too much).
I never use those plastic seal installers deals unless I am installing the hard 100% Teflon seals.
Because it's necessary with the tension rings.