Tvheadend

Hi again
Thanks to Prof Yaffle pointing out my mistake not enabling the damn interface (doh!) I now have the system almost perfect. BUT
I've got a few channels on muxes that are reported as FAIL. What conditions cause a fail?
Is it likely to be a hardware issue (its Compro S350 board, which used to work with Mythtv and picks up the channels in scan)

Any thoughts appreciated.