difficulty 8 bypass unbreaking enchantment

Please read the tooltip text of Diff 8 through 10. This is working as intended.

Also EMC's Unbreaking formula is modified from Vanilla.

Code:

int j = EnchantmentManager.getEnchantmentLevel(Enchantment.DURABILITY.id, this);
int k = 0;

j = Math.min(5, j); // EMC
for (int l = 0; j > 0 && l < i; ++l) {
    // EMC start - make Unbreaking scale to level for armor. 5 = 80% chance of no loss.
    if (getItem() instanceof ItemArmor) {
        if (random.nextFloat() >= 1 - (.8 * (j / 5))) {
            k++;
        }
        continue;
    }
    // EMC end

It takes Unbreaking 5 to get 80%, so 3 will not give 75%

Also the wiki is wrong on Vanilla Unbreaking, as there is a 60% chance that Unbreaking doesn't even kick in for armor on vanilla, and then if it does kick in, its random again from there:

This is vanilla logic:
return itemstack.getItem() instanceof ItemArmor && random.nextFloat() < 0.6F ? false : random.nextInt(i + 1) > 0;

It does not ignore unbreaking. You're misunderstanding how unbreaking works (due to bad information on the Minecraft Wiki). Unbreaking works PER DAMAGE POINT. It is not a % chance to take no damage at all.

On EMC, Unbreaking 3 has a 48% chance per point.

So if an item was to take 10 damage in 1 hit, you could expect 5 damage with unbreaking 3 on average. On Unbreaking 5, it would average 2 damage points.

Then, on Difficulty 8, damage is x2, so you will instead take the original 10 damage.

Again, EMC unbreaking is actually more powerful than Vanilla - The wiki is just flat out wrong.

It's 75% * 40% = 30% for Unbreaking 3 in Vanilla. EMC Unbreaking 2 is actually more powerful than Vanilla 3.