Yeah, I’m going to go with…
Getting hit increases your armor by 50%, but reduces your movement speed by 15% and attack speed by 20%. This effect stacks up to 5 times.
At 5 stacks this means your armour is increased by 250%, but your movement speed is reduced by 75% and your attack speed is reduced by 100%.
This comes up so frequently in the Bug Report forum that it’s in the stickied threads…
…and despite that we’ve still had in excess of 50 threads about it.