I just give up where the Aura is concerned. When coming out of normal or low power standby I get a black screen. I can play recordings, use apps etc. but no live TV. I have to pull the power lead in order to get live functions. It makes no difference whether I start the Aura before or after selecting the HDMI input. This has only started to happen over the last few weeks.
I get this occassionally, but just powering off with the remote or using the Freeview button sometimes clears it, other times I get a screen of static.