When I try to give myself a custom item (with different attributes) in this version, it crashes my game, but only when i put my cursor on the item. Here's an example (Sorry the command is quite long) :

/give @p diamond_sword{display:{Name:"[{\"text\":\"Supreme God Sword\",\"italic\":false,\"color\":\"dark_blue\",\"bold\":true}]",Lore:["[\{\"text\":\"\",\"italic\":false}]","[\{\"text\":\"This Sword is stronger than the God Sword\",\"italic\":false}]","[\{\"text\":\"Most powerful weapon avaible\",\"italic\":false,\"color\":\"dark_gray\"}]"]},Enchantments:[\{id:"fire_aspect",lvl:2},\{id:knockback,lvl:1}],Unbreakable:1,HideFlags:4,AttributeModifiers:[\{AttributeName:generic.attack_damage,Amount:13,Operation:0,UUIDLeast:62281700,UUIDMost:99,Slot:mainhand,Name:generic.attack_damage},\{AttributeName:generic.max_health,Amount:20,Operation:0,UUIDLeast:62281800,UUIDMost:99,Slot:mainhand,Name:generic.max_health},\{AttributeName:generic.movement_speed,Amount:0.03,Operation:0,UUIDLeast:62281900,UUIDMost:99,Slot:mainhand,Name:generic.movement_speed}]} 1

As you can see, I changed the attributes names (such as generic.attackDamage -> generic.attack_damage), but the game also crashes on a custom item I didn't change and which worked on the previous versions.