That circlip can become 'bent out' ... meaning its not holding itself close enough to the shaft anymore, which makes it a [language filter smackdown] to put back on.
Driveshaft places have a tool that puts new clips on, that are a tighter fit. That may help if your exiiting circlip is giving you the shits. I had a similar issues with the pass side shaft on my U13 Bluebird. Had to balance the clip dead centre of the shaft, and pray... then push it in VERY carefully so it cleared the lip inside the spline race.