Greetings from Melbourne!
I owned the Ethos before, ran it with several kinds of amplifiers, from CJ, Mac, VTL and Audio Note Overture. It was superb vfm! Probably ML's best offer in terms of value within this particular range. Of course their new Masterpiece series is superior but so is the price tag!
Anyway, I never had any of these issues with the panels, mine were purchased brand new and obviously sold used only after a year... so not sure why you're panels are playing up. Is it for every type of music ?
Have you tried unplugging the Ethos from the AC mains only, and leaving it off for a few minutes, then power up again.
Also remember important *NOTE*
Always plug in the power cords into the Ethos first and last plug in the power cords into your AC mains, not the other way round! The owner's manual clearly explains this and if you plug in the Ethos end last whiles the AC mains is active...this can cause early panel issues because it prematurely activates the main amplifiers without an audio signal.
It's like plugging in any electrical appliance, so always plug in the unit and last plug in the "pins end" onto your AC mains, either directly to the wall or into a power board. I'm thinking you should already know this...
The Ethos should have a standby light, which is a Red LED, means panel is off and on Standby mode. Then when an audio signal is applied that LED blinks and changes into Blue indicating ready to go... this will happen upon primary turn on or when your Ethos are plugged in for the first time. If this standby - power on & ready Blue LEDs are not working in sequence then you have a problem.
May need to contact Audio Active ( Aus importers for ML) they can offer tech support or contact John Hall, the ESL whisperer... very difficult to get hold of though. I've got his contact number, let me know if you need it.
All the best, RJ