Steps to reproduce:
Place down a light block.
Change the light level of the block.
It appears that one texture (for example, the level 15 texture) and the next texture (for example, the one for level 0) are rendered at the same time.
Β I was able to reproduce this on four different devices:
My main PC (Intel Core i7-10700 and RTX 3060)
My M1 MacBook Pro (Apple M1)
a Lenovo ThinkPad E490 (Intel Core i5-8265U and Intel UHD Graphics 620)
a HP EliteBook 745 G6 (AMD Ryzen 5 3500U and AMD Radeon Vega 8)
Β
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Comments 4

I know that it takes a few seconds to update. The bug is that the textures seem to overlap for a few seconds while it is updating, like in the screenshot below (the picture-in-picture toast is there because this is a screenshot of one of the linked videos).
[media]Β That block looks like the light level 0 texture is on top of the level 15 one.
Duplicate ofΒ MC-47660. This is due to the light particles taking time to disappear.

Thank you for your report!
We're tracking this issue in MC-47660, so this ticket is being resolved and linked as a duplicate.
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Mine update but not immediately. It takes a few seconds for each change.
/give @p minecraft:light