@HelpFixDecoApp thanks a lot for the advice. I'll try that too, although I reckon the issue is most likely caused by some problem between the ISP router and my main Deco BE85 directly connected to...

My home network consists of my Internet Service Provider's router and three Decos in Access Point (AP) mode: two Decos BE85 (hardware version 1) and one Deco BE65 (hardware version 2). The main Deco...