In use lead's (on bunnies at least) are invisible on game start.
A bunnie is connected to a post by a lead.
If you exit the world and come back in, the bunnie is still connected to the post, but the lead is invisible. you can see the lead on the post, but the rest of the rope is invisible.
To reproduce the glitch, just restart the world.
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Looks like this is a very, very old bug (MC-14826).
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I would say so too, except it happens every time, not just at random, and the lead doesn't actually break, just dispersers.
galaxy_2alex
Duplicate of MC-14826