I wish I could tell you.
This was a randomly generated world straight from a server load
There are no server mods
Took the world save to single player and destroyed the Carrot button tree without any crashes then replaced the multiplayer save with the single player save and all appears to be working now
Harry S i am having the same problem, i have tried all of the tricks, i am missing a the tmp file and cannot get it as it has just disappeared, and have reinstalled minecraft to no avail. so your not alone