what if you try a live record?
I would suggest you check out the recording schedules and clear them (I've seen similar issues with mine - but only a reformat sorted it), if this isnt the issue then if it's your box (not a ****** sub) then I'd suggest a reformat - if it is a subbed box then I would make sure you can replicate the issue reliably and then get them out to sort it (as u aint supposed to know how to format it etc lol)