When you crouch, you do not have a "smooth" animation. It works properly in 1.7, but not in the latest snapshots.
This happens in any gamemode.
I made a short video to demonstrate:
http://www.youtube.com/watch?v=ADmFPrw2hUo&feature=youtu.be
Linked issues
is duplicated by 5
Comments 24
Being fixed in 1.7.9 doesn't count as fixed, if the bug was in the 1.8 snapshots. Bug isn't present in any 1.7.x version, but bug is present in 1.8 snapshots starting from 14w06a and through the current 14w11b.
Take a look at MC-35750 does this describe your problem? Does the workaround/resolution work for you?
The issue on MC-35750 is when a person moves while crouching and experiences glitchy movement, but this issue is more referring to the animation of crouching itself. Different versions affected too. The workarounds from there didn't address this one.
Fixed in 18w07c, relates to MC-248996
Is this still a concern in the current Minecraft version 14w11b / Launcher version 1.3.11 or later? If so, please update the affected versions in order to best aid Mojang ensuring bugs are still valid in the latest releases/pre-releases.