CR-10S X-axis error at start of print

My Creality CR-10S gives an odd displacement in the X-axis when starting a print. In the photo, I should have a skirt of width 3, but X has become displaced between the three lines, hence the three spaced-out lines at the ends. X travel appears smooth, with no apparent slipping or loose wiring. Any ideas as to what is causing this? It was doing this from time to time, now it’s doing it all the time. Thanks.