I had good luck when Token Hammer arrived, it was probably one of the best events for me.
I was able to upgrade the following equipment successfully: (+10) (1 ~ 15 attempts Ea.)
x2 Bow of Storm, x2 Flattery Robe, x1 KoSC
x1 CloakOfSurvival, x1 Surv. Circlet, x2 FAW
x1 ImperialSpear, x1 PileBunkerS, x1 EtranUndershirt
x1 ImmuneShield, x1 MadBunny, x1 Work Cap
x1 Tornado Axe, and maybe a few more, I do not remember.
The majority required few attempts, only 1 bow of storm and 1 Cloak of Survival required approximately 15, I think it is only RNG, although I must admit that sometimes I had problems upgrading equips to +9, few, but yes, that's why I think some specific equips are "Cursed".