I'm trying to create a copy of our live DNN (version 8.4.2) on my local as part of an upgrade project. I cannot get to the bottom of the following error. Can anyone throw some light on this?

2018-06-20 07:57:31,511 [IT-Dev01][Thread:7][FATAL] DotNetNuke.Web.Common.Internal.DotNetNukeHttpApplication - System.NullReferenceException: Object reference not set to an instance of an object.    at DotNetNuke.HttpModules.OutputCaching.OutputCacheModule.OnResolveRequestCache(Object sender, EventArgs e)    at System.Web.HttpApplication.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()    at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)    at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)