I reckon the "grey blank box" will be a thumbnail from the recording (given a reboot) rather than a channel logo - at least that's what other Humax PVRs do. Try playing one, and then see what the grey box looks like afterwards.
You are right the channel logos should be in that box. It’s another annoying bug that still hasn’t been sorted.
If you press the freeview play button then go along to players. Once that has loaded press up to the ‘i’ then press + you will then be able to delete the cookies. Once that had been done you should see the channel logos.
I usually have to do this every day, just occasionally they are already there..... but not often.