I had a similar problem a few months ago with a Panasonic DMR-EX 75. It still received analogue signals so was more puzzling. Luckily there is a very reasonable repair man locally and he found some faulty soldering joints or some such in the digital TV tuner power supply. Repair was , I think, about £80 but worked fine ever since.
Hands-on: Acer Predator Triton 700 review