Happens at times. I would like to provide you more information than this but it's what I got.

Failed to call hook 'OnPlayerInit' on plugin 'AdminRadar v4.5.4' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.AdminRadar.HasAccess (BasePlayer player) [0x0004c] in <855e4243ef464299a950134cff3e4144>:0 
  at Oxide.Plugins.AdminRadar.OnPlayerInit (BasePlayer player) [0x0008a] in <855e4243ef464299a950134cff3e4144>:0 
  at Oxide.Plugins.AdminRadar.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x003a2] in <855e4243ef464299a950134cff3e4144>:0 
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <9affce1cd15c4ec183941adef8db1722>:0 
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <4452f821def6406d834e4149849fe7ea>:0 
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <4452f821def6406d834e4149849fe7ea>:0 

Hey, 

Yes this is still an issue. Happens from time to time and I can't see any pattern. It gets NREd even though no Admin is on the server.