2 packages always error on download even from proget web ui

We get an internal server error downloading 2 of our packages. Any version of those packages fail but all other packages are fine. I copied the error below and just removed servername and package name from the logs. This is one of our own packages and is configured the same as any other so we are having issues working out why proget dislikes these 2 packages.
Logged: 2/8/2017 7:37:03 PM Level: Warning Category: NuGet API Message: An error occurred processing a GET request to http://xxxxxxxx:1521/nuget/Opal/package/yyyyyyy/2.0.7: Object reference not set to an instance of an object. Details: at Inedo.ProGet.WebApplication.SimpleHandlers.NuGet.NuGetApi.GetHandler.StripSymbols(Stream packageStream) at Inedo.ProGet.WebApplication.SimpleHandlers.NuGet.NuGetApi.GetHandler.<TransmitPackageAsync>d__1.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Inedo.ProGet.WebApplication.SimpleHandlers.NuGet.NuGetApi.GetHandler.<ProcessGetRequestAsync>d__0.MoveNext() --- End of stack trace from previous location where exception was thrown --- at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task) at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task) at Inedo.ProGet.WebApplication.SimpleHandlers.NuGet.NuGetApi.<ProcessRequestAsync>d__6.MoveNext()

Product: ProGet
Version: 4.6.7

Based on the stack trace, the error is occurring while the symbols are being stripped from the package. This involves opening the package file and inspecting contents... so my guess is that it is a problem with the package. It could be a corrupt zip, or something?

If you're not able to figure out what's wrong with the package, you'll need to send it to us in a support ticket so we debug it further.

thanks we managed to find it as nuget was packing the release and debug files over the top of each other for some stupid reason in just the packages generated for this project. no idea why it did not affect any other solution on our build server