Azure web apps throws error Merging of ETL files has failed - azure

Question

We have an azure website with two instances. .net core 2.1.1 with ef core and some other basic dependencies. From time to time one of the instances gets in a corrupted state and starts throwing 500 on every request.
The error logged in application insights is very low level so it seems to happen in the framework or "below" our code. Recent changes is moving from 2.1.0 to 2.1.1, implenting azure key vault, configuration of signal-R.
The first error below seems to be suggesting a problem with application insights and "ApplicationInsightsProfiler"
There is not a specific way to reproduce but it seems to start throwing the error when we are using our biggest request which create a lot of db-queries.
Any ideas on what can cause this or maybe some ideas on how to tack what can cause this error?
Second error (that is thrown all the time after the first initial error)
System.IndexOutOfRangeException:
at Go7 (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Text.RegularExpressions.CompiledRegexRunner.Go (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Text.RegularExpressions.RegexRunner.Scan (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Text.RegularExpressions.Regex.Run (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Text.RegularExpressions.Regex.IsMatch (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Text.RegularExpressions.Regex.IsMatch (System.Text.RegularExpressions, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Data.Common.DbConnectionOptions.ValidateKeyValuePair (System.Data.Common, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Data.Common.DbConnectionStringBuilder.set_Item (System.Data.Common, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Data.SqlClient.SqlConnectionStringBuilder.set_Item (System.Data.SqlClient, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Data.Common.DbConnectionStringBuilder.set_ConnectionString (System.Data.Common, Version=4.2.1.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Data.SqlClient.SqlConnectionStringBuilder..ctor (System.Data.SqlClient, Version=4.4.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerConnection.get_IsMultipleActiveResultSetsEnabled (Microsoft.EntityFrameworkCore.SqlServer, Version=2.1.1.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
at Microsoft.EntityFrameworkCore.Storage.RelationalConnection+<Microsoft-EntityFrameworkCore-Storage-IRelationalConnection-RegisterBufferableAsync>d__61.MoveNext (Microsoft.EntityFrameworkCore.Relational, Version=2.1.1.0, Culture=neutral, PublicKeyToken=adb9793829ddae60)
First error: Merging of ETL files has failed (0x80070507) (Flags: 0x0000011f).
System.Runtime.InteropServices.COMException:
at DiagnosticsHub.StandardCollector.Host.Interop.ICollectionSession.Stop (ApplicationInsightsProfiler, Version=2.4.60711.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at Microsoft.ServiceProfiler.Collectors.StandardCollectorBase.<StopAndCollectAsync>b__10_0 (ApplicationInsightsProfiler, Version=2.4.60711.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)
at System.Threading.Tasks.Task`1.InnerInvoke (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089)
at System.Threading.Tasks.Task.Execute (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089)
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089)
at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification (mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089)
at Microsoft.ServiceProfiler.Collectors.DetailedTraceCollector+<StopCollectingAndSaveTrace>d__26.MoveNext (ApplicationInsightsProfiler, Version=2.4.60711.2, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a)

Answer 1

Developer on Application Insights Profiler here.
The first error is a known bug that we have fixed in version 2.6.5 of the Application Insights site extension. Use the Azure Portal to upgrade the site extension on your web app(s).
However, I note that you are using .NET Core 2.1; there is currently another bug affecting .NET Core 2.1 applications which results in no profiling data being collected. We have a fix for that, but it has not yet been released.
I don't know about the 2nd error. It's probably unrelated to the profiler.