Mu-so QB Volume Control Light

The only times I've seen mine do that is when it's trying to either connect to the network (I use wireless on mine) or, when my Internet has gone down and it's unable to connect, for example, to iRadio.

Thank you @blythe I guess the same, it might be a connectivity issue, yet it continues playing properly. It stopped flashing after some 15 mins. 

Depending on what source music you're playing, it might continue playing. For example, if you're listening to upnp music stored on a NAS drive, your internet going down won't pause the music.
I have a few wifi access point on the network I use and I had occasional issues where the QB would connect to a slightly less strong signal access point.
In the end, I changed the SSID of the one closest to the QB and reset it to always connect to that stronger network.

Thank you for reply Blythe. I will check whether it will continue or not.