This can sometimes happen if your original recording did not complete correctly.

Or if you've set a 'Series Link' recording (which will record an entire series) and find multiple recordings of the same episode, it’s likely that the broadcaster has set the same series ID but a different programme ID for repeat broadcasts of an episode.  

If that’s the case, please note down the title of the programme, the episode in question, the date and time it was broadcast / recorded and contact the broadcaster so that scheduling information can be corrected for future episodes.