Whenever breaking a block then in the middle switch to another item in your inventory it stops the block from breaking.
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Comments
CubeTheThird
Of course it stops breaking...
This is intended.
Duplicate of MC-2519
kumasasa
Thanks, Tails.
When I tried this, at first the behaviour was as you described. But if I started breaking the block a second time, after it should have broken, it breaks instantly.