Just had a look and this issue with Technika TVs doesn't seem to be included on the YouView forum's "Consolidated List of Bugs and Faults", which leads me to suspect it may indeed be a Technika problem. You could try the workaround suggested by Graham. I would add, it may be worth doing this from scratch: connect with Scart not HDMI; do a factory reset; set the YouView box and TV both to 1080i; then try your HDMI connection.
I'm belatedly mindful that this YouView issue doesn't belong in this thread so might be as well to start a new thread for any further comments. Apologies to the OP.
