X axis jump away from print job

[kiteroom 0]

I'm running Cura 2.3.1 on a Prusa I3. I've tried printing a couple of designs off thingyverse with odd results. In both cases the print starts fine then later the X axis moves away from the print to the left, at the same height, and prints in the air. Looking through the gcode I don't see an X value that explains this.

Has anyone else seen this?

[goppae 1]

i have the same problem! what can we do?

[ultiarjan 1,223]

probably a hardware issue? loose pulley? does it look like this?

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#shifted