Signs, banners, skulls and chests are flashing when item spawner is nearby

Some signs (banners, chests, skulls) are randomly flashing. It's like light changes only for that signs (...) .
it depends on my postion and direction (maybe only other chunks).
I hope the video describes the bug well.
I cant reproduce that for other worlds, but it happens again after a restart for this world.

https://www.youtube.com/watch?v=5SYxlojQKEc

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Steps to reproduce:

• Place some signs, banners, chests, skulls
• Place an item spawner

  /setblock ~ ~ ~ minecraft:mob_spawner 0 replace {SpawnData:{id:Item,Item:{id:"minecraft:iron_ore"}}}

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Code analysis by Marcono1234 is found here