I have found a bug or more of a broken interaction between two items.
The gloves Boulderfist have a special effect, “You cannot leach health”. However, the 1h axe Undisputed has an effect of leeching percentage of overkill damage. From the wording of both items, it would seem like the gloves should prevent the life leech from the axe but they don’t. They seem to prevent all other life leech that I have come across except for this one.