To reproduce:
Turn on Toggle Sprint
Find a mob
Perform a critical hit chain without pressing A or D keys, and click rapidly while doing so
You'll notice your player's movement resets very frequently. This occurs similarly during PvP combat in a world or Bedrock Dedicated Proxy, where your opponent's movement appears to teleport frequently when you are dealing knockback.
Side note: hence, is it possible to implement Java 1.8 Knockback or 1.9 Knockback (assume full cooldown) to Bedrock Dedicated Proxy?
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This issue is being tracked at MCPE-189501.