Failed to call internal hook 'Unload' on plugin 'ServerRewards v0.4.77' [4006810030] (Object reference not set to an instance of an object)
   at void Oxide.Plugins.ServerRewards.SaveRP() in /home/container/carbon/plugins/ServerRewards.cs:line 3627
   at void Oxide.Plugins.ServerRewards.Unload() in /home/container/carbon/plugins/ServerRewards.cs:line 1498
   at object Oxide.Plugins.ServerRewards.InternalCallHook(uint hook, object[] args) in ServerRewards.cs/Internal:line 923

Looks like a framework issue, not a plugin issue.