On my death by an NPC I received this error.. 

I was downed by bradley, then rushed by NPC spawned in with BotReSpawn if that helps.
on the death screen it showed my prior death, and there was no new death marker on the map. 
Is this an Oxide issue, or is it more likley  to be a plugin?

Failed to call hook 'IOnBasePlayerAttacked' on plugin 'RustCore v2.0.5439' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000fb] in <50629aa0e75d4126b345d8d9d64da28d>:0

  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <50629aa0e75d4126b345d8d9d64da28d>:0

Stomping old lifeStory << this came straight after it.

Unfortunately it's hard to tell where the error is coming from, as the actual error is being hidden. Easiest way to figure out what is causing the error would be to check which plugins are using the OnEntityTakeDamage and remove them individually to test.

Cheers Wulf, I will do that and se if I can track it down.. appreciate the advice. :)