We have recently upgraded a website from v6 to v7.10 and are now seeing regular errors in the error logs:

2018-08-08 17:41:57,240 [25] ERROR Umbraco.Core.UmbracoApplicationBase [(null)] - An unhandled exception occurred


System.InvalidOperationException: This operation is not supported for a relative URI.
   at System.Uri.get_PathAndQuery()
   at ClientDependency.Core.CompositeFiles.Providers.BaseCompositeFileProcessingProvider.WritePathToStream(ClientDependencyType type, String path, HttpContextBase context, StreamWriter sw) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\Providers\BaseCompositeFileProcessingProvider.cs:line 209
   at ClientDependency.Core.CompositeFiles.Providers.CompositeFileProcessingProvider.<>c__DisplayClass2_0.<CombineFiles>b__0(String s) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\Providers\CompositeFileProcessingProvider.cs:line 74
   at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
   at System.Linq.Enumerable.WhereEnumerableIterator`1.MoveNext()
   at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
   at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
   at ClientDependency.Core.CompositeFiles.Providers.CompositeFileProcessingProvider.CombineFiles(String[] filePaths, HttpContextBase context, ClientDependencyType type, List`1& fileDefs) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\Providers\CompositeFileProcessingProvider.cs:line 74
   at ClientDependency.Core.CompositeFiles.CompositeDependencyHandler.GetCombinedFiles(HttpContextBase context, String fileset, ClientDependencyType type, List`1& fDefs) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\CompositeDependencyHandler.cs:line 254
   at ClientDependency.Core.CompositeFiles.CompositeDependencyHandler.ProcessRequestInternal(HttpContextBase context, String fileset, ClientDependencyType type, Int32 version, Byte[] outputBytes, OutputCachedPage page) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\CompositeDependencyHandler.cs:line 185
   at ClientDependency.Core.CompositeFiles.CompositeDependencyHandler.System.Web.IHttpHandler.ProcessRequest(HttpContext context) in C:\Users\Shannon\Documents\_Projects\ClientDependency\ClientDependency\ClientDependency.Core\CompositeFiles\CompositeDependencyHandler.cs:line 110
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStepImpl(IExecutionStep step)
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)

We have no idea what is causing the errors or how to reproduce it - which makes fixing it a problem.

Does anyone have any ideas?