What I expected to happen was...

When I attack a player with a knockback resistance armor piece, they take less knockback on a scale.

What actually happened was...:

When I attacked a player, say with 50% knockback resistance, they would take 50% less knockback (so far correct), but also have a 50% chance to not take knockback  (which I don't believe is intended).

Steps to Reproduce:

1. Have a player wear a chestplate with knockback resistance on it. I used

   /replaceitem entity @p armor.chest leather_chestplate{AttributeModifiers:[{AttributeName:"generic.knockback_resistance",Name:"generic.knockback_resistance",Amount:0.5,Operation:0,UUID:[I;42853,1689024593,-201178,-1559272105]}]}

2. Have another player hit the player wearing the chestplate several times (the problem is more easily seen when using an item with knockback on it)
3. Some of the time the player with the chestplate will take half (assuming 50% knockback resistance, which shows as 5 in the description and is 0.5 in the command) the amount of knockback, while other times they will take no knockback.