Kazoo & Bubble upnp loses 272 renderer

I am using Linn Kazoo on windows to control my 272, and bubble upnp does the transcoding and proxying. Often Kazoo looses connection to the 272 - i.e. it cannot see the 272 renderer. It seems to correspond with the computer running Kazoo sleeping (it loses connection after I wake it up) and the only solution I have found is to restart the bubble upnp server. Then everything works again. Is there any way I can stop kazoo losing connection with the renderer?

I am lost for ideas, so any help will be gratefully received.