To reproduce:

setup repeating, always-active command block with:

/execute at @a[nbt=\{SelectedItem:{id:"minecraft:stick",tag:{display:{Name:"\"black\""}}}}] run particle minecraft:squid_ink ~ ~ ~ 1 1 1 1 3000 force

(the particles are just visuals, every command works)

then give yourself this stick:

/give @p minecraft:stick{display:{Name:"\"black\""}} 1

and select it in your hotbar

your vision will go black which is fine but then press E to open your inventory and you'll see the particles disappear. As soon as you open your inventory the stick nbt data seems to be changed, affecting the name of the item. Not visually but technically which is why the command then fails.

Does not happen in vanilla or different plugin configurations.

Does happen in the newest versions of spigot aswell