I'm sure this is easy when you know how, but i can't figure it out so...

Everything works fine for a few hours. Then the connection is lost. If I do something externally (like trigger a pin with a button) OR force communication with the 'X' i get comms again.
Polling is like this:
What am I doing wrong? Do i need to periodically send data from the Z-Uno with the sketch or can this be handled in some better way?
Best regards,
Eric