We suggest using non-ISP routers from a reputable brand - TP-Link/ASUS/Netgear/Eero/Orib all have some great options. There are also a few router suggestion threads on the forum. Having a non-ISP router can potentially save you some trouble down the road.
You can still use the ATT modem/router in what is called “Bridge Mode”, and have it just act as a modem (coax -> ethernet) and then have a better router handle the rest of the routing.
That is very strange indeed. If you notice another set of albums with the same behavior, can you please try to play them and let me know the exact local time + date + track you tried to play and had the failure? Afterwards I can enable diagnostics mode for your account and see if logs show any clues.