It happened to me a lot of times, that an instrument broke off my robotic arm, by bringing the arm back to it's initial position.

How about a emergency soft-stop and a hard stop feature?

soft-stop = arm/mast operation stopped because of danger to break off instruments, other parts of the rover and/or whole robotic arm's head.

All other operations like driving, working with other parts of the rover, are not affected.

Movement of arm or mast is just possible to move the arm/mast out of the soft stop zone.

hard-stop = arm operation stopped and fully canceled.

All other parts, are stopped and locked, too. All parts of the rover have to be set manually to their initial position.

Rover has to be reset after that (Rebooting sequence, with chance of losing the rover/lander)