At approx 27 mins when a file is being burnt in an incinerator, the sticker on the file in the front top right hand corner with the person's details is clearly seen to burn to ash. Later when Barnaby retrieves the file the sticker is fully intact and untouched, the only burn is a smouldering circle below it.
Dr. Bullard hands DCI Tom Barnaby a DNA report on John Ransom. Barnaby drops it on the counter, grabs his coat and briefcase, and walks away talking to DS Scott. In the next shot, the report is back in DCI Barnaby's right hand, though the counter is several feet behind him.