[Backpacks] Error when saving player backpack 76561############:
System.UnauthorizedAccessException: Access to the path "/home/container/oxide/data/Backpacks/76561############.json" is denied.
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) [0x0019e] in <f98723dd4586469db5213ec59da723ca>:0
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.IO.FileOptions options) [0x00000] in <f98723dd4586469db5213ec59da723ca>:0
at (wrapper remoting-invoke-with-check) System.IO.FileStream..ctor(string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int,System.IO.FileOptions)
at System.IO.StreamWriter..ctor (System.String path, System.Boolean append, System.Text.Encoding encoding, System.Int32 bufferSize) [0x00055] in <f98723dd4586469db5213ec59da723ca>:0
at System.IO.StreamWriter..ctor (System.String path) [0x00008] in <f98723dd4586469db5213ec59da723ca>:0
at (wrapper remoting-invoke-with-check) System.IO.StreamWriter..ctor(string)
at System.IO.File.WriteAllText (System.String path, System.String contents) [0x00026] in <f98723dd4586469db5213ec59da723ca>:0
at Oxide.Core.Configuration.DynamicConfigFile.WriteObject[T] (T config, System.Boolean sync, System.String filename) [0x0003f] in <112d89ea5d3348c8b949af0ab1a866d2>:0
at Oxide.Plugins.Backpacks+Backpack.SaveIfChanged () [0x00055] in <3641226b8dd841459a00b0e6f6d4a338>:0
at Oxide.Plugins.Backpacks+BackpackManager+<SaveAllAndKill>d__38.MoveNext () [0x000a1] in <3641226b8dd841459a00b0e6f6d4a338>:0
[Backpacks] Error when saving player backpack 76561############:
System.UnauthorizedAccessException: Access to the path "/home/container/oxide/data/Backpacks/76561############.json" is denied.
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) [0x0019e] in <f98723dd4586469db5213ec59da723ca>:0
at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.IO.FileOptions options) [0x00000] in <f98723dd4586469db5213ec59da723ca>:0
at (wrapper remoting-invoke-with-check) System.IO.FileStream..ctor(string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int,System.IO.FileOptions)
at System.IO.StreamWriter..ctor (System.String path, System.Boolean append, System.Text.Encoding encoding, System.Int32 bufferSize) [0x00055] in <f98723dd4586469db5213ec59da723ca>:0
at System.IO.StreamWriter..ctor (System.String path) [0x00008] in <f98723dd4586469db5213ec59da723ca>:0
at (wrapper remoting-invoke-with-check) System.IO.StreamWriter..ctor(string)
at System.IO.File.WriteAllText (System.String path, System.String contents) [0x00026] in <f98723dd4586469db5213ec59da723ca>:0
at Oxide.Core.Configuration.DynamicConfigFile.WriteObject[T] (T config, System.Boolean sync, System.String filename) [0x0003f] in <112d89ea5d3348c8b949af0ab1a866d2>:0
at Oxide.Plugins.Backpacks+Backpack.SaveIfChanged () [0x00055] in <3641226b8dd841459a00b0e6f6d4a338>:0
at Oxide.Plugins.Backpacks+BackpackManager+<SaveAllAndKill>d__38.MoveNext () [0x000a1] in <3641226b8dd841459a00b0e6f6d4a338>:0

This isn't something I can resolve. This could happen to any plugin that tries to write data files. You'll have to troubleshoot file system permissions on your server.