SF Press (NPC Horse) Script Error

Sometimes this script error is shown after using the PRESSNPC:

System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.ArgumentException: An item with the same key has already been added.

  at System.ThrowHelper.ThrowArgumentException(ExceptionResource resource)

  at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue value, Boolean add)

  at OpenSim.Region.PhysicsModule.BulletS.BSScene.AddAvatar(UInt32 localID, String avName, Vector3 position, Vector3 size, Single footOffset, Boolean isFlying)

  at OpenSim.Region.Framework.Scenes.ScenePresence.AddToPhysicalScene(Boolean isFlying)

  at OpenSim.Region.Framework.Scenes.ScenePresence.StandUp(Boolean addPhys)

  at OpenSim.Region.OptionalModules.World.NPC.NPCModule.Stand(UUID agentID, Scene scene)

  at OpenSim.Region.ScriptEngine.Shared.Api.OSSL_Api.osNpcStand(LSLString npc)

  at OpenSim.Region.ScriptEngine.Shared.ScriptBase.ScriptBaseClass.osNpcStand(LSLString npc)

  at SecondLife.XEngineScript.clearUp() in c:\Use

It doesn't occur during each use so it's difficult to determine the cause.

Thanks for reporting this. Someone else did report it a while back but I have not yet managed to get that error so hard to pin down. I do see i the error report it mentions x-engine so wonder if that may be an issue as I use y-engine now (since the next main release will, I believe, drop x-engine)

Do you know if that's what your region uses?

Did not expect this but my regions were on x-engine. (I use DreamGrid and it was set to the default, which I thought was y-engine).
I've since switched and restarted everything, but now some machines aren't working properly. Added products show as "missing", the windmill gives a "bad password" error, and product counts are not increased when added to storage. Am a bit befuddled on this one...

When you switch engines you need to shut down the region, make the changes and then delete everything in the folder ..opensim/bin/ScriptEngines  before restarting.  Hope that makes sense for Dreamgrid. If not there may be an option somewhere to clean out that stuff? 

Ah... Thanks for the tip. It might be the script cache... I'll check around and find out. Thanks again.

Have same issue I was the one that reported it a while back changing script engine did not help. I likes it but can't use it.