There is nowhere for the robot to put the tape that is in the drive after dismount - this is why the drive keeps going down.
Someone has inserted tapes in all the slots while a tape (from slot 5) was in the drive.
Messages file:
Sep 19 12:51:07 his1 tldcd[23394]: TLD(0) cannot dismount drive 1, slot 5 already is full
Sep 19 12:31:59 his1 tldcd[22193]: TLD(0) closing/unlocking robotic path
Sep 19 12:31:59 his1 tldd[21813]: DecodeMount: TLD(0) drive 1, Actual status: Unable to SCSI unload drive
Open the robot, remove the tape in the drive, then inventory.
Else, remove all tapes, use robtest to unload drive and move tape to slot 5.
Inventory robot.
Add more tapes, then Inventory.
PS:
In fututure, please copy the text in cmd output, rather than taking screenshots?