(Sorry for broken formatting on the commands–I can't figure out how to fix it. Just remove the line breaks to fix it.)

Running

/give @p minecraft:elytra{AttributeModifiers:[

{AttributeName:"minecraft:generic.armor",Slot:"chest",Operation:0,Amount:3.0d,UUID:[I;-1623373971,-1055374012,-2090507132,1761916046]}

]}

will disconnect the player with the following error screen:

Rejoining the server will result in the same error. The player is NBT-banned from the server due to the lack of the Name property in the attribute modifier object. This issue does not occur in vanilla. This command, in contrast,

/give @p minecraft:elytra{AttributeModifiers:[

{AttributeName:"minecraft:generic.armor",Name:"any text here",Slot:"chest",Operation:0,Amount:3.0d,UUID:[I;-1623373971,-1055374012,-2090507132,1761916046]}

]}

works fine in Spigot, as it is not missing the Name property.