Cannot rename a file in uno WASM Platform

I have a uno app where I can rename a file using uno UWP but the same code does not rename the file when build against the uno WASM platform.

I am getting the list of files in a folder using a StorageFolder object.

StorageFolder SourceFolder = new FolderPicker();
ObservableCollection<StorageFile> SourceFiles = new SourceFiles();
IReadOnlyList<StorageFile> files = await SourceFolder.GetFilesAsync();
foreach(StorageFile sf in files)
{
    SourceFiles.Add(sf);
}

SourceFiles are then bound to a ListView

<ListView x:Name="imagelist" ItemsSource="{Binding SourceFiles}".../>

At a later point in the app I have a button to rename selected items in the ListView.

The Code behind looks like this:

int imageNumber = 0;
foreach(var item in imageList.SelectedItems as StorageFile)
{
    imageNumber++;
    string newname=$"{imageNumber}.jpg";
    if (item is StorageFile sf)
    {
        await sf.RenameAsync(newname);
    }   
}

This works in UWP but in WASM it appears to hang at the RenameAsync method. The foreach loop never progresses.

I am wondering if the IReadOnlyList is the problem in WASM but not in UWP. Is there something that I can do differently?