Bukkit

What steps will reproduce the problem?
1. Have ClayGen running in farming mode on a Spigot 1.7.2 server for about 30 minutes. Default timing configuration for ClayGen. (50 seconds)

What is the expected output? What do you see instead?

Clay should continue to generate from gravel, it stops after approx. 30 minutes.

What version of the product are you using?

1.7 with a Spigot 1.7.2 R0 server.

Do you have an error log of what happened?

The following exception is generated:

[22:46:11] [Thread-12/WARN]: Exception in thread "Thread-12"
[22:46:11] [Thread-12/WARN]: java.lang.IllegalStateException: Asynchronous entity world add!
[22:46:11] [Thread-12/WARN]:     at net.minecraft.server.v1_7_R1.World.a(World.java:2465)
[22:46:11] [Thread-12/WARN]:     at net.minecraft.server.v1_7_R1.Chunk.addEntities(Chunk.java:742)
[22:46:11] [Thread-12/WARN]:     at net.minecraft.server.v1_7_R1.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:131)
[22:46:11] [Thread-12/WARN]:     at net.minecraft.server.v1_7_R1.ChunkProviderServer.getChunkAt(ChunkProviderServer.java:88)
[22:46:11] [Thread-12/WARN]:     at org.bukkit.craftbukkit.v1_7_R1.CraftWorld.getChunkAt(CraftWorld.java:118)
[22:46:11] [Thread-12/WARN]:     at org.bukkit.craftbukkit.v1_7_R1.CraftWorld.getBlockAt(CraftWorld.java:82)
[22:46:11] [Thread-12/WARN]:     at org.bukkit.craftbukkit.v1_7_R1.block.CraftBlock.getRelative(CraftBlock.java:170)
[22:46:11] [Thread-12/WARN]:     at org.bukkit.craftbukkit.v1_7_R1.block.CraftBlock.getRelative(CraftBlock.java:178)
[22:46:11] [Thread-12/WARN]:     at org.bukkit.craftbukkit.v1_7_R1.block.CraftBlock.getRelative(CraftBlock.java:174)
[22:46:11] [Thread-12/WARN]:     at Tux2.ClayGen.ClayGen.hasBlockNextTo(ClayGen.java:590)
[22:46:11] [Thread-12/WARN]:     at Tux2.ClayGen.ClayGen.run(ClayGen.java:480)
[22:46:11] [Thread-12/WARN]:     at java.lang.Thread.run(Thread.java:722)

Please provide any additional information below.

I've looked up the exception (and how it relates to Spigot) and found this thread:

http://www.spigotmc.org/threads/asynchronous-entity-add.3526/ with a link to this wiki page: http://wiki.bukkit.org/Scheduler_Programming#Tips_for_thread_safety

Would switching from farming mode to instant conversion avoid this async issue for now?