I am running Spigot 1.8.7, and the Stargate will not open. It will light up, but will not dial. I went and checked to see if it works with Craftbukkit on the same version, and it does.
Here is the error message:

[20:26:55 WARN]: org.apache.commons.lang.UnhandledException: Plugin WormholeXTreme v1.1 generated an exception while executing task 343
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.IllegalStateException: Asynchronous block remove!
at org.spigotmc.AsyncCatcher.catchOp(AsyncCatcher.java:14)
at net.minecraft.server.v1_8_R3.Block.remove(Block.java:317)
at net.minecraft.server.v1_8_R3.Chunk.a(Chunk.java:536)
at net.minecraft.server.v1_8_R3.World.setTypeAndData(World.java:396)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setTypeIdAndData(CraftBlock.java:137)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setTypeId(CraftBlock.java:130)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setType(CraftBlock.java:121)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setType(CraftBlock.java:116)
at de.luricos.bukkit.WormholeXTreme.Wormhole.model.Stargate.animateOpening(Stargate.java:207)
at de.luricos.bukkit.WormholeXTreme.Wormhole.logic.StargateUpdateRunnable.run(StargateUpdateRunnable.java:121)
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftTask.run(CraftTask.java:71)
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
... 3 more

[20:26:55 WARN]: Exception in thread "Craft Scheduler Thread - 3"
[20:26:55 WARN]: org.apache.commons.lang.UnhandledException: Plugin WormholeXTreme v1.1 generated an exception while executing task 342
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:56)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)
at java.lang.Thread.run(Thread.java:722)
Caused by: java.lang.IllegalStateException: Asynchronous block remove!
at org.spigotmc.AsyncCatcher.catchOp(AsyncCatcher.java:14)
at net.minecraft.server.v1_8_R3.Block.remove(Block.java:317)
at net.minecraft.server.v1_8_R3.Chunk.a(Chunk.java:536)
at net.minecraft.server.v1_8_R3.World.setTypeAndData(World.java:396)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setTypeIdAndData(CraftBlock.java:137)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setTypeId(CraftBlock.java:130)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setType(CraftBlock.java:121)
at org.bukkit.craftbukkit.v1_8_R3.block.CraftBlock.setType(CraftBlock.java:116)
at de.luricos.bukkit.WormholeXTreme.Wormhole.model.Stargate.animateOpening(Stargate.java:207)
at de.luricos.bukkit.WormholeXTreme.Wormhole.logic.StargateUpdateRunnable.run(StargateUpdateRunnable.java:121)
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftTask.run(CraftTask.java:71)
at org.bukkit.craftbukkit.v1_8_R3.scheduler.CraftAsyncTask.run(CraftAsyncTask.java:53)
... 3 more