I have just got a Play 5 and connected it to my TV's headphone port to the line in port on the play 5. The sound works fine coming out of the Play 5 (a little static feedback but nothing major). However, I have added my two Play 1s to the 'group' to create a surround sound effect and the sound keeps dropping in and out on the Play 1s. There doesn't seem to be a specific pattern to the drop out and it is only momentary before the sound resumes but it's enough to make the setup unusable. If the sound on the Play 5 dropped as well then I would know it is something wrong with the connection to the TV but the sound on the Play 5 is fine.
Any thoughts as to what could be wrong?