EPTFor example, a liberator attack 2 corruptors hit by AAM (all without any upgrade), the targeted corruptor receives (5-2+3)*2 = 12 damage per hit, and the other receives only (5-2)*2 = 6 damage per hit though both them show as (2-3) armor.
If a thor attacks several observers stack together that hit by AAM, the first volley will kill only 1 observer, while all the rest have 12 HP left.
A 0/0 baneling will NOT kill any zerglings with carapace upgrade but hit by AAM.
This bug applies to all circle-type aoe attack, including Liberator, Thor's AA, siege tank in siege mode, planetary fortress, archon, ultralisk and baneling. Colossus, hellion, hellbat and lurker are not affected. Units attacked by them all receive correct extra damage.
It seems that the real mechanism of AAM is that the game engine calculate the damage taken without AAM first, if the attack is either melee or range, but not splash damage, it simply adds 3 damage to the target unit.
I made another test using a 0 upgrade mutalisk against 3 fully upgraded ultralisks. The mutalisk's bounce damage is 3 and 1, but it actually does 3.5 damage per hit against the second and third ultralisks though they all showed as (7-4) armor, which is still 4.
I believe the most impacted unit is Liberator, because its AA weapon has a relatively large aoe radius but low damage per attack. When against corruptors, 3*2 = 6 damage from 6*2 = 12 damage is 100% difference.
I also found a video (https://www.bilibili.com/video/av64981058) on a Chinese website which the author demonstrate 6 more bugs he found:
1.Carrier’s interceptors attack faster against a retreating unit from behind.
2.Hydralisk melee attacks faster than ranged attack. (Hydralisk uses another weapon and animation against melee target. In patch 4.2.0, Hydralisk’s attack speed is nerfed, but they only changed range attack’s weapon speed, and forget to change its melee weapon’s attack speed.)
3.Beam-type weapon (such as oracle, void ray，sentry and mothership) will attack faster when switching target. This bug is known to Blizzard. They tried a fix, bug it did not work well and they were forced to revert the fix.
4.The attack speed of beam-type weapon will not affected by any means, such as Mothership’s Time Stop, Co-op and Campaign’s Energizer’s chrono beam or units attacked by Vile Roach. For example, a sentry will attack at exactly same speed inside a Time Stop bubble.
5.The leading unit does not collide with any units that follow it. It may just walk through those following units.
6.A charging zealot after it begins to charge but before it hit the target can be manually switch to charge another unit much farther away, while keep the charging state for about 20 range.
