Itemstacks serialized in yaml before:
==: org.bukkit.inventory.ItemStack
{{ v: 2584}}
{{ type: DIAMOND_BOOTS}}
{{ meta:}}
{{ ==: ItemMeta}}
{{ meta-type: UNSPECIFIC}}
{{ display-name: 'Jump Boots'}}
{{ lore:}}
{{ - 'Increases Jump'}}
{{ - 'Increases Speed'}}
{{ - ''}}
{{ - 'Jumps: 10'}}
{{ enchants:}}
{{ PROTECTION_ENVIRONMENTAL: 5}}
{{ DURABILITY: 5}}

Itemstacks now:
==: org.bukkit.inventory.ItemStack
{{ v: 2584}}
{{ type: DIAMOND_BOOTS}}
{{ meta:}}
{{ ==: ItemMeta}}
{{ meta-type: UNSPECIFIC}}
{{ _display-name: '{"extra":[}}

{{

{"bold":false,"italic":false,"underlined":false,"strikethrough":false,"obfuscated":false,"color":"green","text":"Jump Boots"}

}}

],"text":""}'_
{{ lore:}}
{{ _- '{"extra":[}}

{{

{"bold":false,"italic":false,"underlined":false,"strikethrough":false,"obfuscated":false,"color":"green","text":"Increases Jump"}

}}

],"text":""}'_
{{ _- '{"extra":[}}

{{

{"bold":false,"italic":false,"underlined":false,"strikethrough":false,"obfuscated":false,"color":"green","text":"Increases Speed}

}}

],"text":""}'_
{{ - ''}}
{{ _- '{"extra":[}}

{{

{"bold":false,"italic":false,"underlined":false,"strikethrough":false,"obfuscated":false,"color":"green","text":"Jumps: 10"}

}}

],"text":""}'_
enchants:
PROTECTION_ENVIRONMENTAL: 5
DURABILITY: 5

This wouldn't be a problem except that the line break "- ''" isn't read and results in the line break being removed when loaded. Please convert all - '' lines to - '{"text":""}' to fix this.