Automatic Speaker Switch issue when audio signal turns off

I'm attempting to use this switch to enable my in-ceiling speakers to take input from both my sonos system (Sonos Port -> External Amp -> switch -> Speakers) as well a channel from my AVR.

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I'm testing the switch just using 2 different amp channels, to see how it works.

What i've found is that when the "B" channel input (which takes precedence when detected) to the switch automatically switches off at the amplifier, the switch gets confused and goes into a loop where the relay clicks on/off repeatedly - sometimes for 5 seconds, sometimes until i power off the switch.

This also happens if i just power off the amp completely (so, no audio signal to either switch input). In that case I can hear the relay click over maybe 6-8 times, then stop.

I've adjusted the sensitivity down as far as I can where it will still detect an active "B" channel signal - that seemed to help the scenario where I power off the entire amp, but still happens when the B channel turns off.

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Am I doing something wrong? Did I just buy a crap switch? Are these types of switches reliable/usable in general. Ideally this would be hidden away in a basement server rack somewhere so it's not like I could easily pull the power plug, need something that's close to 100% reliable.
Appreciate any suggestions, thanks