Confirming it is easily able to be reproduced most of the time by going far enough away for the chunk to unload. Note that this for the lead actually breaking, not the invisible lead problem. I am unsure as to why the breaking problem is being closed as duplicates.
Been getting this since 1.6.1. I thought it was a SMP issue but it have been happening extremely often in my current SSP world as well (1.6.2).
I think this may be the same thing. I am not sure so I am including my crash log. I was just exploring new terrain and it crashed with this error.
[pastebin - ticking error|https://pastebin.com/Z4BnJnnE]
ed: it crashes within a few seconds when loading the world now, same error. i'll just wait for a new prerelease before trying to load it again
Thanks for your time.