In Survival LAN play and SSP, I was able to duplicate leads (not 100% of the time) by leashing a pig, then pushing it through a nearby nether portal. Sometimes it would drop a lead without consuming one of the two I was using.
Over the course of 5ish minutes experimenting, I was able to turn two leads into four.
Related issues
is duplicated by
MC-16031
Leads duplicate if they are attached to an mob entering the nether
MC-16642
Lead Dupe Bug
MC-19026
Lead duplication
MC-19049
[Horse Lead Duplication Bug]
MC-19568
Duplicating Leads
MC-65622
Lead duplicating when pushing horse through nether portal
MC-65742
Lead duplication glitch
MC-66530
Dupe Bug
MC-69758
Duplicate Bug
MC-70923
Lead Duplication
MC-71784
Lead Duplication
MC-74307
duplicating leads when going through portal
MC-75653
Leads can be duplicated
MC-75880
Copying Lead
MC-79981
Leads Duplicate When Sending a Leashed Animal Through a Portal
MC-81081
Nether Portal Lead Duplication
Comments
migrated
galaxy_2alex
Reopened, happens again
MC-65622
migrated
I can confirm this issue is still ongoing in the latest 1.8-pre1 release. I can duplicate leads 100% of the time. For example, if I bring 2 animals into the nether on leads, then go back to the over world, I am able to pick up 4 usable leads.
migrated
Confirmed still ongoing in 1.8
migrated
This issue occurs in Minecraft version 1.8.1 as well. It is consistently reproducible in single player 1.8.1.
Attach two cows to two leads. Push them through the nether portal. Enter the nether portal. The leads duplicate on the ground on the other side.
wobst.michael
Cannot reproduce in 16w41a
migrated
What about 1.10.2?
This appears to be back in 14w31a. Lead a horse through a nether portal from the overworld by walking around the portal (horse went through and I didn't). I then went through the portal and couldn't find the lead so I went back to the overworld. Upon arriving, I ended up with 2 leads. I can push the horse through with the same results.