We are running umbraco 7.3.1 on azure web apps. 1 backoffice node and 4 front-end nodes. Lately we have been seeing umbraco-plugins.list errors in our elmah logs.

System.IO.IOException
The process cannot access the file 'D:\home\site\wwwroot\App_Data\TEMP\PluginCache\umbraco-plugins.RD000D3A31301C.list' because it is being used by another process.

System.Web.HttpUnhandledException (0x80004005): Exception of type 'System.Web.HttpUnhandledException' was thrown. ---> System.IO.IOException: The process cannot access the file 'D:\home\site\wwwroot\App_Data\TEMP\PluginCache\umbraco-plugins.RD000D3A31301C.list' because it is being used by another process.
   at System.IO.__Error.WinIOError(Int32 errorCode, String maybeFullPath)
   at System.IO.File.InternalDelete(String path, Boolean checkHost)
   at System.IO.File.Delete(String path)
   at Umbraco.Core.PluginManager.UpdateCachedPluginsFile[T](IEnumerable`1 typesFound, TypeResolutionKind resolutionType) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\PluginManager.cs:line 431
   at Umbraco.Core.PluginManager.LoadViaScanningAndUpdateCacheFile[T](TypeList typeList, TypeResolutionKind resolutionKind, Func`1 finder) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\PluginManager.cs:line 745
   at Umbraco.Core.PluginManager.ResolveTypes[T](Func`1 finder, TypeResolutionKind resolutionType, Boolean cacheResult) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\PluginManager.cs:line 708
   at Umbraco.Core.PluginManager.ResolveAttributedTypes[TAttribute](Boolean cacheResult, IEnumerable`1 specificAssemblies) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\PluginManager.cs:line 785
   at Umbraco.Web.WebBootManager.<InitializeResolvers>b__a() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\WebBootManager.cs:line 348
   at Umbraco.Core.ObjectResolution.LazyManyObjectsResolverBase`2.<Initialize>b__5(Func`1 x) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\ObjectResolution\LazyManyObjectsResolverbase.cs:line 155
   at System.Linq.Enumerable.<SelectManyIterator>d__16`2.MoveNext()
   at System.Collections.Generic.List`1.InsertRange(Int32 index, IEnumerable`1 collection)
   at Umbraco.Core.ObjectResolution.LazyManyObjectsResolverBase`2.<Initialize>b__3() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\ObjectResolution\LazyManyObjectsResolverbase.cs:line 155
   at System.Lazy`1.CreateValue()
   at System.Lazy`1.LazyInitValue()
   at System.Lazy`1.get_Value()
   at Umbraco.Core.ObjectResolution.LazyManyObjectsResolverBase`2.get_InstanceTypes() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\ObjectResolution\LazyManyObjectsResolverbase.cs:line 183
   at Umbraco.Core.Macros.XsltExtensionsResolver.CreateInstances() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\Macros\XsltExtensionsResolver.cs:line 36
   at Umbraco.Core.ObjectResolution.ManyObjectsResolverBase`2.<InitializeAppInstances>b__0() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\ObjectResolution\ManyObjectsResolverBase.cs:line 142
   at System.Lazy`1.CreateValue()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Lazy`1.get_Value()
   at Umbraco.Core.ObjectResolution.ManyObjectsResolverBase`2.get_Values() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Core\ObjectResolution\ManyObjectsResolverBase.cs:line 253
   at umbraco.macro.GetXsltExtensions() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\macro.cs:line 1128
   at umbraco.macro.AddMacroXsltExtensions() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\macro.cs:line 1139
   at umbraco.macro.GetXsltTransformResult(XmlDocument macroXml, XslCompiledTransform xslt, Dictionary`2 parameters) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\macro.cs:line 1044
   at umbraco.macro.LoadMacroXslt(macro macro, MacroModel model, Hashtable pageElements, Boolean throwError) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\macro.cs:line 964
   at umbraco.macro.renderMacro(Hashtable pageElements, Int32 pageId) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\macro.cs:line 446
   at umbraco.presentation.templateControls.Macro.CreateChildControls() in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\umbraco\templateControls\Macro.cs:line 186
   at System.Web.UI.Control.EnsureChildControls()
   at umbraco.presentation.templateControls.Macro.OnInit(EventArgs e) in c:\projects\umbraco-cms-xtjqd\src\Umbraco.Web\umbraco.presentation\umbraco\templateControls\Macro.cs:line 120
   at System.Web.UI.Control.InitRecursive(Control namingContainer)
   at System.Web.UI.Control.InitRecursive(Control namingContainer)
   at System.Web.UI.Control.InitRecursive(Control namingContainer)
   at System.Web.UI.Control.InitRecursive(Control namingContainer)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.HandleError(Exception e)
   at System.Web.UI.Page.ProcessRequestMain(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest(Boolean includeStagesBeforeAsyncPoint, Boolean includeStagesAfterAsyncPoint)
   at System.Web.UI.Page.ProcessRequest()
   at System.Web.UI.Page.ProcessRequestWithNoAssert(HttpContext context)
   at System.Web.UI.Page.ProcessRequest(HttpContext context)
   at ASP.default_aspx.ProcessRequest(HttpContext context)
   at System.Web.HttpApplication.CallHandlerExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute()
   at System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously)