If the paper is printing at a slight angle then that would suggest that the rollers are slipping on the media. This can happen when using smooth or glossy media like labels.
To fix the problem you can try cleaning or replacing the rollers with a new roller kit. Cleaning the rollers is simple enough. All you need is an alchohol based cleaning solution and a lint free rag or swab. Open up the printer and clean any of the contact rollers around the paper tray. Clean them both up and see if it helps.
I would also test printing on normal paper for your label print jobs. If the normal paper prints find then you have confirmed there is a slipping issue. Either get the rollers to grip with the above suggestions or find a different sheet of labels to print with that are better suited to the pickup rollers of this printer.