Grass dies under partial, transparent blocks such as fences, buttons, grindstones, pots, trapdoors, doors chains, etc. when the grass should be able to grow underneath. The grass dies in a low light level and when a block is above it, it will only grow back in light. While the grass growing back in light makes sense, the grass should not die when these blocks are placed on top.
Some partial blocks just kill grass no matter the light level, while on Java edition they don't, such as the anvil.
Current list of blocks: Fence, Trapdoor, Door, Sign, Wall, Plant pot, lightning rod, anvil, structure void, chain, button, grindstone, and pressure plate.
Steps to Reproduce:
Place one of the partial blocks above a grass block
Set time to midnight
/time set midnight
Place any full block 3 blocks above the grass
Either wait, or increase random tick speed
/gamerule randomtickspeed 1000
Linked issues
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Comments 3

This appears to be a very similar issue to some other reports such as; MCPE-135043 MCPE-113306 MCPE-62132 MCPE-113305 MCPE-116758 but these only specific cases of some blocks and do not address that the block is covered from above.