Unless they've changed things, anything over about 140 luck before enhancing is a guaranteed failure or break (0% success chance) even with 120 Smith and a +60 ASH.
Tailoring, because of there being no equivalent to an ASH, is around 130 Luck where 0% success chance hits - but since only Physical is changed with spined, the failure chance is just based on two variables.
All the other crafting skills used for enhancing are capped at 100 skill, and often change more than one other property, so the maximum Luck before it's 0% success is somewhere around 120.
However, I do believe that there are occasional glitches in the matrix (where somehow the code is broken and a 9% success chance hits). I actually enhanced something once (a shield) by accident (targeted the wrong item, without using my forged metal tool first) that should have been impossible (the chance of success should have been 0% for luck, as the failure chance.
The formula for luck enhancing is Failure chance = Current Luck/2+30%.
However, you then multiply it by the success chance of each other attribute being changed. The examples below use tailoring as that's the easiest and most simple skill for the material that gives luck. metals and woods, IIRC, add other properties.
So, if there's a 20% at 100 luck to enhance to 140 (100/2+30=80 failure chance, so success is 20%), and you're enhancing a tailor armor item with Physical resist 20% at a point where there's only a 60% chance of success (40% chance of failure), then the chance of success is 20% x 60% = 0.2 x 0.6 = 0.12 = 12%.
If the luck started at 140, and the Physical was 2% (the base minimum), that would be Luck (100% -(140/2+30)) x Physical (100% -(20+2) = 0 x 78%. And ANYTHING times Zero is ZERO.
Depending on where the (added sometime after ML) +1% bonus per 10 points over 100 is added, it might make a difference. We've never heard for sure.
If added at the "each chance", then the 140 luck example at 120 skill becomes (0+2%) x (78+2%) = 2% x 80% = 1.6% (but would drop to less than 1% chance at 142 luck, and go back to 0% at 144 luck).
If added after the final calculation, then the 140 luck example at 120 skill becomes (0 x 78%)+2% = 0% + 2% = 2%.
However, given that so many +x% bonuses in the past have proven to be a multiplier, not an addition*, even a 102% multiplier to a 0% chance is STILL ZERO.
* (such as how fish bait is "103% x rare fish chance" instead of "rare fish chance +3%" and the elven 20% colored ore bonus is "human chance x120%" instead of "Human Chance +20%")