Whenever errors like these occur, there is not much you can do since it's usually associated with the robotics.
First step, always try to update the firmware to the latest version (for both the library and and the tape drives). Then, instead of just letting it restart, fully shut off the unit.
When troubleshooting these issues, just for the heck of it, I'll also take a backup of the config and perform a factory reset (just to see if this clears anything). Keep in mind that when it's in an error state, usually you will not be able to save the config from the web interface, because of this, I always keep a copy of config for all the MSL's I manage.
Last step, make sure that the clear plastic peices in the magazine are seated properly and that they are clean. Also, try re-seating the tape drive. I know that re-seating the tape drive is somewhat un-related. But there's been issues I've dealt with in the past where shutting it down, removing, and reinsterting the tape drive have fixed odd robotic related errors.
If this doesn't solve it, chances are it's the robotics and you'll need to put in a warranty request to get the chassis replaced.
