I've seen one possible explanation noting that since the lens has a stepper motor, it could lose synch with the camera body, and a remount/restart is needed to get the camera to synch up again. The fix may very well be just having the camera body do a synch when the lens position does not match rather than lockup or generate a error message.
I tried another thing after reading the comment, focusing far away, then keeping my finger on the lens barrel so it could not move out to focus closely. I could feel the stepper motor pulsing for about 5 seconds, then I removed my finger and it focused fine. I also manually pushed it in while focusing, it just keeps working fine.
Could those with a problem mention the body they are using?