Intermittent noise issue on ZD3+ZA3 combo

[sbiehe]

Hello

I have a ZD3 connected via HDMI to a Sony LCD TV and via a TOSLINK to a Chromecast Audio. The ZD3 is driving two ZA3's in mono mode through RCA cables. The ZD3 controls the ZA3's through its 12V output trigger.

• For the first hour or so, the system plays just fine but after some time, an intermittent clicking noise appears in the left speaker only.
• I have attached an audio recording of the noise to this post.
• If I disconnect the RCA cable between the ZD3 and the le,ft ZA3, the problem disappears.
• If I disconnect the 12V triggers, the problem persists.
• If I disconnect the HDMI cable, the problem persists.
• If I replace the Chromecast Audio with the USB output of a laptop and switch the ZD3 to USB input, the problem persists.

To me, this points to a problem with the ZD3, what do you think?