06:49 [Error] Web request produced exception (Url: https://api.steampowered.com/ISteamRemoteStorage/GetPublishedFileDetails/v1/) (NullReferenceException: Object reference not set to an instance of an object)
at Oxide.Core.Libraries.WebRequests+WebRequest.<WaitForResponse>b__40_0 (System.IAsyncResult res) [0x00000] in <bae5f1223fce49c493b01571c99dce02>:0

The error is hole bing in a plugin you are using web requests with. You'd need to see which plugin is calling that URL to find the culprit.