Advanced installer in version 18.6 autodetects the wrong references for a simple C# project that contains a reference to the gRPC nuget package.
The path to the nuget packages uses the compile time dll under "...\nuget\packages\<some package>\ref\..." instead of the runtime dll under "...\nuget\packages\<some package>\lib\..."
That wrong path is autogenerated into the *.aip file.
Manually fixing those references in the *.aip file and building the installer via Developer Command Prompt "msbuild MyInstaller.aiproj" works around this issue and produces an installer with the correct dll files.
After building the project you can look at obj/project.assets.json to see that the dlls differ between compile and runtime for some dependencies of gRPC like System.Buffers.dll
See the attached zip for an example project.