the item you want to up have to be max dura, else artisan wont up it for you
also after each failed try your item will lose 50% of its dura,
you can upt items till 60 without worrying abt fails (at least never happened to me)
after 60 it may start failing
and getting a sock is still ranom, i dont really believe in any theories,
only thing i would believe is maybe the thing of raisnig Chance if failing with Dbs, since TQ only gives a **** to Dbs, cuz they want ppl buy em