That's pretty rare, in my experience- I think I've broken one J45 treble string -the high 'e', as well- in over thirty years of on-and-off usage (mostly on) of them, and I attribute that to the way I tied it.
Maybe look for a sharp edge at the nut, saddle, or tie block to start.
Adding: when you attach a treble string to the tie block, wind it around itself
at least twice, and make sure the final wind is on the *back side* of the tie
block, not on top. Pull out all the slack at that time, then thread it through
the string roller per usual; again minimizing slack rather than having many
winds around the roller. That's what works for me, anyway.
