Gear doesnt degrade at the same rate. So won't be repaired to the same % when you self repair either as self repairing adds 100%, so one at 50% will repair to 150%, another piece at 70% will repair to 170%. Then obviously the 1st piece will hit <100% sooner.

Just checked my alt who I dont have crafts high enough to self repair, from 100% and running LCoA.
All left side except chest at 86%, chest at 91%, right side all @82%