Luckily I have network equipment which can tell me why there was a problem (Cisco Meraki). And I only see one SSID from my neighbours (2.4 GHz is not congested).

Initially I had two Access Points balancing connections, the same SSID broadcasted both 2.4 GHz and 5 GHz, auto channel, a/b/g/n/ac w2. I had all kinds of errors and it was a pain to troubleshoot.

What I did was to broadcast a specific SSID just for the squeezeboxes that is static channel 1, only 2.4 GHz and is only broadcasted from one single access point.

Now I've narrowed it down to a DHCP problem, where the squeezebox stops working after half of the lease time. I have 24 hours lease time, SB stops working after 12 hours. This is when I have Fixed IP configured.

It seems the only choise for me that is working is to set a Static IP on the device and reserve that IP in the DHCP range.

One other option, to assign dynamic DHCP, works for a week until DHCP pool is full (seemingly full of fake squeezeboxes).