Failed to call hook 'OnPlayerInput' on plugin 'Build v2.0.83' (NullReferenceException: )
  at (wrapper managed-to-native) UnityEngine.Component.get_transform(UnityEngine.Component)
  at Oxide.Plugins.Build+PlayerBuild.Execute () [0x00017] in <3fad1e16d1f2449cb6dd575d965bd250>:0
  at Oxide.Plugins.Build.OnPlayerInput (BasePlayer player, InputState state) [0x00105] in <3fad1e16d1f2449cb6dd575d965bd250>:0
  at Oxide.Plugins.Build.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x000c2] in <3fad1e16d1f2449cb6dd575d965bd250>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <80b90e8213db44b29ec2d4111764172c>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <ec05e0208c9149bba43236ca58fea105>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <ec05e0208c9149bba43236ca58fea105>:0 

[Oxide] 14:16 [Error] Failed to call hook 'OnPlayerInput' on plugin 'Build v2.0.83' (NullReferenceException: Object reference not set to an instance of an object)
  at Oxide.Plugins.Build+PlayerBuild.Execute () [0x00079] in <53be3c863d2042eaa80e9e4990445a55>:0
  at Oxide.Plugins.Build.OnPlayerInput (BasePlayer player, InputState state) [0x00105] in <53be3c863d2042eaa80e9e4990445a55>:0
  at Oxide.Plugins.Build.DirectCallHook (System.String name, System.Object& ret, System.Object[] args) [0x000c2] in <53be3c863d2042eaa80e9e4990445a55>:0
  at Oxide.Plugins.CSharpPlugin.InvokeMethod (Oxide.Core.Plugins.HookMethod method, System.Object[] args) [0x00079] in <3606d2af539c45e4b5c61658e6a8b307>:0
  at Oxide.Core.Plugins.CSPlugin.OnCallHook (System.String name, System.Object[] args) [0x000d8] in <c2afd8354b8b4f3ca451cf5a1aa111c3>:0
  at Oxide.Core.Plugins.Plugin.CallHook (System.String hook, System.Object[] args) [0x00060] in <c2afd8354b8b4f3ca451cf5a1aa111c3>:0

looks like the rust update changed the grade parameter from number to string.