MP4/Web Object on Layer Plays First Time Only

I inserted a Web Object onto a layer in Storyline, pointed it to an external MP4 using an absolute URL, and access it using a hyperlink to Show the layer. This works, the video clip plays, but if I Hide the layer and then return to it, the video clip will not play again. In fact, nothing but a big blank appears in the space reserved for the video. Is there a work-around which will allow me to continue referring to an externally-hosted MP4, rather than embedding the video clip into Storyline? Or is this a known bug?