Players turn on/off at random

Not sure where to post this as I'm not sure where the fault lies, and its not restricted to one type of player, but I'm finding that SB3 and Boom devices which are on standby (dimmed) seem to spring into life apparently at random (screen text lights up & a just-audible pop is heard on SB3 where attached amp is also on), then go back into standby (dimmed) again a second or so later.

Any idea what's going on here and how to stop it? Could some plugin be responsible?