When you and another player leash two different invisible entities(in my case two different chickens) they are leashed correctly, but there is another leash connecting the two entities that should not be there. See first image. (You can see the two chickens and their leashes connected to them. But then there is an extra leash(the really long one) that should not be there and is only visible when the entity is invisible)

Steps to reproduce

• Spawn a chicken
• Make it invisible
• Leash it
• Go to the second account
• Spawn a second chicken
• Make it invisible
• Leash it
• Make sure both players are visible, and you will see the line connecting the two that should not be there

 Note: It is not always visible. You either need to look around to see it or relog on the server.