HomePod Mini activates randomly

Hi, I have 2 HomePods Mini, I have used it almost 2 years as stereo set paired with Apple TV and iPhone XR. One day I noticed that one of HomePod Minis is randomly switching / activating and answering me like I told something and/or played some tunes from Apple Music without my intention. I have heard that it can be caused by dirt on touch surface, so solution was to clean touch surface and set up "longer touch" commands through accessibillity menu. I have done it and also found that there was some update fw for Mini, so I made this too. Everything went as it has to and after few hours it activated itself again. The other Mini is OK. All happened in quiet room in the middle of the night, which was really disturbing. I made reset of the HomePod Mini, but the problem wasn't solved. also I tried more resets and few times it was claiming with red rotational lights that "to reset, hold up to 3 sec..." and restarted itself, so it was in some dead cicle error. I took the cable off the wall and left it few days, tried it again and pairing was successful, but with same ghosting randomly time by time claims "I cannot find it... but I ca search the web for you, would you like me to open it on your iPhone?"... or sometimes just lights were blinking like it's listening, but no one intended any sound or claim "hey Siri". Is there any solution or it has to go to service? Thank you in advance