Hello,
Same problem here (DM8000 SST) when zapping from S-tuner to T-Tuner.
Sometimes "Tune Failed", but pictures comes after a couple of seconds.
or
"Tune failed" messages appears and there is no image at all. At this point there is no image on all T-channels.
Only zapping to S-Tuner and then back to T-Tuner brings the image back.
The most evil thing is that my recordings on T-channels are often unusable too. (.ts file with zero length)
Regards,