Probably due to the changes made for https://bugs.mojang.com/browse/MC-156013
Client velocity is reset (due to the new packet being sent) when you do the following:
move (so that the velocity reset becomes visable)
start digging a block (that isn't yet broken before switching to the next one in the next step)
while keeping the dig button pressed: look over to a neighboured block that is instantly breakable (grass, flowers, netherrack with an efficiency pickaxe, etc.)
-> velocity is reset
The easiest way to set this up is by going over a field with grass (or an effiency 5 pickaxe and netherrack, starting with a block that is not instantly mineable with a pickaxe -> not instantly mineable block next to an instantly mineable block)
Linked issues
is duplicated by 6
MC-156258
Instant Mine Stuttering
Resolved
MC-156450
Stuttering movement when mining blocks
Resolved
MC-156471
While breaking grass pieces the players character will stutter and stop in their tracks
Resolved
MC-156476
Lagging Back When Breaking Crops
Resolved
MC-156513
Sudden stops while breaking sugarcanes.
Resolved
1 more links
Nassim Jahnke
Fry
Adding my video from the duplicate bug report here too, to show how this can be easily reproduced by breaking crops and looking at the dirt below.
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