I'm having the same issue.
I'm using docker on Windows , image: proget.inedo.com/productimages/inedo/proget:latest

dotnet nuget push .\MyPackage.snupkg -k "<mykey>" --source http://localhost/nuget/meulocalsymbols

As @john-selkirk said it just silently fail.

If I try to send both at the same time, only de nupkg is sent.

dotnet nuget push .\MyPackage.nupkg -k "<mykey>" --source http://localhost/nuget/meulocal --symbol-source http://localhost/nuget/meulocalsymbols

I've discovered this project today, but I think that I understood the idea of having two different feeds one for package (meulocal) and one for symbols (meulocalsymbols). The first one I didn't check "Enable symbol and source server for this feed" and the second one I've checked.

Thanks in advance!