Hi,
I have now reset the tv to factory and performed a system reset on the T8. Having done this I immediately went into screen resolution and it was set at 1080p. 720 and 480 were also displayed. I have tried all four HDMI ports on the tv but can only get 1080p from the T8 mini. All of this is with the latest firmware with android 6.
Having already tested the HDMI cable with a friends 4k blu-ray on my Tv, which works, I can only assume there is an issue with the initial handshake from the T8 mini.
Apart from this issue the T8 is a very good piece of kit. Shame Droidbox dont seem to have a solution.