In the end - it seems my problem is that I'm using a second router as a repeater - and it seems to be handing out leases while keeping the original network name. For now I'm turning off that router when booting up important devices, and then turning ...
My modem is not consistently giving IP leases to devices - and strangely the device is online, but the lease is not visible through admin app, and the IP is not reachable through ping or otherwise (which is causing problems as e.g. my phone sound sys...