I've got this problem too, my safe is +4 and it always broke at +5, i've checked the enchantitem.log and this is what is written in.
[07 juin 0:18:50] Success, Character:Irini [268479840] Account:azerty IP:XX.XX.XX.XX, +1 Dynasty Phantom(1) [268480194], Scroll: Enchant Weapon (S)(94) [268479903], 100
[07 juin 0:18:55] Success, Character:Irini [268479840] Account:azerty IP:XX.XX.XX.XX, +2 Dynasty Phantom(1) [268480194], Scroll: Enchant Weapon (S)(93) [268479903], 100
[07 juin 0:19:00] Success, Character:Irini [268479840] Account:azerty IP:XX.XX.XX.XX, +3 Dynasty Phantom(1) [268480194], Scroll: Enchant Weapon (S)(92) [268479903], 100
[07 juin 0:19:05] Success, Character:Irini [268479840] Account:azerty IP:XX.XX.XX.XX, +4 Dynasty Phantom(1) [268480194], Scroll: Enchant Weapon (S)(91) [268479903], 100
[07 juin 0:19:10] Blessed Fail, Character:Irini [268479840] Account:azerty IP:XX.XX.XX.XX, Dynasty Phantom(1) [268480194], Blessed Scroll: Enchant Weapon (S)(48) [268479920], 0
As you can see, at +5 the enchant rate is 0% success.
Any idea to fix it ?
Thx by advance