[Nytingale]

So it appears that so long as you upgrade your weapon at a Blacksmith, Self-Service functions on the weapon's old Durability to calculate at what maximum amount it will check to repair weapons for. I've noticed this occurs to be happening with the Mastery Sub-Path being maxed out as well, so I'm not sure if it works normally without the Sub-Path being used. But basically, if you're Weapon's Durability is 46, instead of Self-Service proc'ing at 90% of 46 Durability (41 Durability or lower), it only procs at 36 Durability or lower; which is, 90% of 40 Durability.