Unable to convert object, no sdk type defined for class

So, this USED to work to return all of the snapshots of all the VM's in a folder (and subfolder):

if (subfolders == true)
    var virtualMachines = System.getModule("com.vmware.library.vc.folder").getAllVirtualMachinesByFolderIncludingSubFolders(vmFolder);
else
    var virtualMachines = System.getModule("com.vmware.library.vc.folder").getAllVirtualMachinesByFolder(vmFolder);
   
var snapshot = new VcVirtualMachineSnapshotInfo();
var allSnaps = new Array();
for (var i in virtualMachines)
{   
    var snapshot = virtualMachines[i].snapshot;
    if (snapshot != null)
        {
            var rootSnaps = snapshot.rootSnapshotList;
            for (var ii in rootSnaps)
                {
                    allSnaps.push(rootSnaps[ii]);
                    GetChildSnapList(rootSnaps[ii]);
                }
        }
}

return allSnaps;

function GetChildSnapList(snap)
{
    var childSnapshotList = snap.childSnapshotList;
    for (var ss in childSnapshotList)
        {
            allSnaps.push(childSnapshotList[ss])
            GetChildSnapList(childSnapshotList[ss])
        }
}

Since the update to 5.1, I get the following error when it returns allSnaps to an array of type VC:VirtualMachineSnapshot

ch.dunes.model.type.ConvertorException: Unable to convert object, no sdk type defined for class : com.vmware.vim.vi4.VirtualMachineSnapshotTree@2f68fe27

Has something changed, and I need to modify the way I am doing this, or is it another bug?