How often it occurs: Often. More present with faster mining tools. Is repeatable with any tool. Likelihood of it occurring reduces when mining speed is closer to vanilla values.
What should happen: The block should break and be collectable.
What Shouldn’t happen:
The block, instead of breaking, breaks client side but server side remains. While other players can see the block, the player who created the ghost block cannot. This causes them to be whip-lashed around, and get stuck. If they are sieging someone and trying to dig in, this happens a lot. It will eventually kick the player, making them loose the siege and loose their items.
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