Hi - I had a Humax for a long time before I got a (so-called) smart TV.
IME the message you get is because the original signal quality is poor - you can ususally check the signal strength for a given channel. Channels are grouped in frequency blocks, so a poorly set-up aerial may work fine for some channels but not others (depending on which MUX/multiplex the channels are on).
I would guess you don't have a hard disk problem, and would only follow this line of attack once you've eliminated tuning/signal problems. Although the hard disks used are physically the same as those used in ordinary PC's the formatting is different (the track and sector information magnetically placed on the disc itself is optimised for AV - audiovisual - use and is not the same as for a PC).
My advice would be to double-check the aerial and its connections (do you get pigeons/gulls sitting on it!?) and to check signal strength - on all channels that you watch - having re-tuned. Probably also to do a "factory reset" on the software - sometimes the settings within the Humax operating software do get mangled (usually by playing "noisy" content like yours with bits missing).
Cheers, W2S