Grass and mycelium don't spread to dirt

What is your gamerule randomTickSpeed set to?

And also, what was the light level? Grass needs light to grow

randomtickspeed was set to 300 and Light Level is 15

I am not able to reproduce this. @unknown Can you upload your world?

Is this still present in the latest snapshot?

Yes :c

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I don´t know, how this works, both ways.

Meanwhile, it´s removed! 😃