Drag and Drop not working when UI is 'Drop Panes' without filters

Edit Subject

I have a Playa field inside a Matrix cell. When I configure the UI mode to be drop panes alone, without filtering, I can't drag the entries between panes.

When I use all of the other options, including using a filter, the dragging works fine. Any ideas what the cause could be?

I should add that Playa fields are working fine in other channels, this only appears to be occurring inside a Matrix cell.