U2723QE, MacBook Pro, randomly goes black

Hi,

I've just bought this monitor and generally very happy with it except randomly goes completely black for a few seconds. Like it has lost power, but the comes back on again. Any ideas anyone as to what might be happening? I've check connections and they seem fine.

HDMI connection via a hub, using MacBook Pro,

AMD Radeon Pro 5500M 8 GB