Where did you interchange the speaker connection? At one end, or at both ends? Have you submitted a system diagnostic within 10 minutes of experiencing this problem, and called Sonos Support to discuss it?
There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.
When you speak directly to the Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.
