Object or property already exists error when trying to export-certificate from root store

I'm trying to export my entire Cert:\CurrentUser\Root\ certificate store to an .SST file. What am I doing incorrectly?

In an administrator's powershell - I'm using:

Get-ChildItem -Path Cert:\CurrentUser\Root\ | Export-Certificate -FilePath C:\certs\test.sst -Type SST.

It returns:

Export-Certificate : The object or property already exists. (Exception from HRESULT: 0x80092005) At line:1 char:46 + ... User\root | Export-Certificate -FilePath c:\certs\allcertasdfs.sst -T ... + ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + CategoryInfo : NotSpecified: (:) [Export-Certificate], COMException + FullyQualifiedErrorId : System.Runtime.InteropServices.COMException,Microsoft.CertificateServices.Commands.ExportCertificateCommand