nre after starting event

Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0
Exception while calling NextTick callback (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Plugins.HCOilrigEvent+<>c__DisplayClass137_0.<NpcsSpawn>b__0 () [0x0004e] in <8d3ce228dc0043a6837fbdc14ff07955>:0
at Oxide.Core.OxideMod.OnFrame (System.Single delta) [0x00051] in <112d89ea5d3348c8b949af0ab1a866d2>:0

Hi, when exactly will this happen? 

shortly after i run hcoestart from console. doesnt seem to happen every time, but happened a few times yesterday when i was setting up the plugin. 

The HardCore Oil Rig Event does not use the Npcspawn plugin. I assume you are using the BetterNpc plugin and it is enabled on the oil rig. That could be the problem. In the next update, I will add a feature that disables BetterNpc during the event.

i am using betternpcs yes

Disabled on Oilrig.