I've never had transfer bar break and I own 6 Ruger SA's that have them as original equipment, most have had thousand of rounds through them, with the exception of a couple of safe queens. I wonder if the transfer bar in the NV the same as the Vaquero, BH, SBH, et al? As in same geometry and same material? Perhaps a new supplier is making them for Ruger? Who knows, sounds to me like manufacturing variance or something. I've stoned and polished a few transfer bars that had some pretty sizable voids in them, which could lead to breaks under repeated use.
God Bless America!