I already had a similar problem. It was due to computer drawer loss of 24V on J213.
The controller was powered with an external 24V, and it happened that this external 24V dropped during robot operation. That was causing the "DSI9 board not referenced error" at reboot.
Maybe if you are in the same configuration it is worth to investigate.
But I don't know if we are in the same situation because, in our case, we could clearly see the teach turn off during the loss of 24V and then reboot