Custom Item Durability Decreases Faster than it Should when Hitting an Entity

Custom items gain damage when hitting an entity faster than they should - approximately 2 damage per hit instead of one.

Steps to reproduce:

• Download the add-on attached to this report
• Apply it to a new world
• Search in the creative inventory for an item called "Grass Sword" with the texture of an egg
• This item has a durability of 15 and therefore should withstand 15 hits
• Try hitting an entity with this item. You will observe that it breaks on the 8th hit.

Expected behaviour:

Custom items should gain one damage per one hit. They are supposed to break after as many hits as is their durability value, specified in the "max_durability" field of the "minecraft:durability" component (assuming the item had not been damaged by other means).

Actual behaviour:

Custom items will break after significantly fewer hits than would be expected given their durability.