We're currently aware of an ongoing problem with "tile entities" duplicating. The reason is really technical, so I'll spare you the details, but the effect is: tick rate slows the server freezes due to "crafting" the server stalls entirely Crafting is not actually slow -- it's this problem. It only affects Nether too, so it baffles me. Over the next week, I will find some time to add some code to the server to diagnose the cause. We can unload Nether to temporarily fix it without restarting the server. Here's a graph of the issue: The gaps are server restarts.
