dotnet publish of a Blazor WASM project errors with An item with the same key has already been added

Really struggling with an issue publishing a Blazor WASM project that is using .NET 6.

Previously, it was on .NET 5, and there were no issues with building / publishing the app.

I've updated it to .NET 6, by essentially updating the nuget references for:

• Microsoft.AspNetCore.Components.WebAssembly (to 6.0.0-rc.2.21480.10)
• Microsoft.AspNetCore.Components.WebAssembly.DevServer (to 6.0.0-rc.2.21480.10)

We've updated to .NET 6 due to a requirement on DynamicComponent

Running locally during development is fine.

During our build pipeline, I am executing the following to publish the app:

dotnet publish .\Web\Web.Connect --configuration debug --output output

The output that I am getting is:

  Web.Connect -> C:\git\core\Web\Web.Connect\bin\debug\net6.0\Web.Connect.dll
  Web.Connect (Blazor output) -> C:\git\core\Web\Web.Connect\bin\debug\net6.0\wwwroot
  Optimizing assemblies for size, which may change the behavior of the app. Be sure to test after publishing. See: https://aka.ms/dotnet-illink
C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks\Microsoft.NET.Sdk.BlazorWebAssembly\targets\Microsoft.NET.Sdk.BlazorWebAssembly.6_0.targets(404,5): error : System.ArgumentException: An item with the same key has already been added. Key: C:\git\core\Web\Web.Connect\obj\debug\net6.0\build-gz\bxkpRzBw.gz [C:\git\core\Web\Web.Connect\Web.Connect.csproj]
C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks\Microsoft.NET.Sdk.BlazorWebAssembly\targets\Microsoft.NET.Sdk.BlazorWebAssembly.6_0.targets(404,5): error :    at System.Collections.Generic.Dictionary`2.TryInsert(TKey key, TValue value, InsertionBehavior behavior) [C:\git\core\Web\Web.Connect\Web.Connect.csproj]
C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks\Microsoft.NET.Sdk.BlazorWebAssembly\targets\Microsoft.NET.Sdk.BlazorWebAssembly.6_0.targets(404,5): error :    at System.Collections.Generic.Dictionary`2.Add(TKey key, TValue value) [C:\git\core\Web\Web.Connect\Web.Connect.csproj]
C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks\Microsoft.NET.Sdk.BlazorWebAssembly\targets\Microsoft.NET.Sdk.BlazorWebAssembly.6_0.targets(404,5): error :    at Microsoft.NET.Sdk.BlazorWebAssembly.ComputeBlazorPublishAssets.GroupExistingStaticWebAssets(Dictionary`2 assemblyAssets, Dictionary`2 nativeAssets, Dictionary`2 satelliteAssemblyAssets, Dictionary`2 symbolAssets, Dictionary`2 compressedRepresentations) [C:\git\core\Web\Web.Connect\Web.Connect.csproj]
C:\Program Files\dotnet\sdk\6.0.100-rc.2.21505.57\Sdks\Microsoft.NET.Sdk.BlazorWebAssembly\targets\Microsoft.NET.Sdk.BlazorWebAssembly.6_0.targets(404,5): error :    at Microsoft.NET.Sdk.BlazorWebAssembly.ComputeBlazorPublishAssets.Execute() [C:\git\core\Web\Web.Connect\Web.Connect.csproj]

Ok - so some asset is trying to be published multiple times in ComputeBlazorPublishAssets?

Found information indicating that adding <ErrorOnDuplicatePublishOutputFiles>false</ErrorOnDuplicatePublishOutputFiles> to the *.csproj might help here, but it has made no difference.

I have ensured that the wasm-tools have been installed via dotnet workload install wasm-tools.

Running a "Publish" via VS 2022 also gives the same error.

I am at a loss as to how I can debug this, or figure out what is getting generated twice, or how to fix this issue.

Thanks.