I've got it to fail on the TV's HDMI 4 so the problem is not specific to HDMI 1. I have been unable to find where to set specific 1080 settings on the TV's HDMI ports.
I'm also struggling to find how to set the DTR-T2100 into Maintenance Mode as I'm not sure where the -vol is on the top of the unit, if it actually has one. I can't find any reference to these buttons in the guide that came with the Youview box nor online. Might be trial and error with the direction buttons around the central OK button. Any ideas?