One player suddenly getting dropouts

For the first time in the 20 months since I replaced my five Sonos players with Bluesound players, one of them is exhibiting dropouts. And it’s the one that is closest to the router. (Approximately 3 metres, with two thin walls in-between.)

I’ve been reading Bluesound Support articles and forum posts, but I’m still rather lost. What should I be looking for?

I’ve been using only the 5 GHz band because, in this building, the 2.4 GHz band is extremely congested. The router is set to “Auto” and currently using channel 161, which is not busy at all, i.e. Wi-Fi Analyzer does not show anyone else using it at the moment, nor the adjacent channel. Should I try to change it anyway? Or restrict the channel width? (It is set to 20/40/80MHz.)

All five players are always grouped together. Only one is hardwired to the network.

The problematic player (Pulse M) currently shows a signal strength of -46 dBm on the Diagnostics screen of the BluOS app. The others are showing -48, -47 and -61.

Approximately 20 minutes after I wrote the above, I checked the signal strengths again and they were all between -45 and -49, i.e. “Excellent”. But the same unit was still sputtering.

I’ve also rebooted the device in question. It hasn’t made any difference.

The problem started when the system was using version 4.12.4 but is persisting even after updating to 4.14.9.