BasicMicro

I have a Roboclaw 2x30 with a potentiometer position encoder.

The limits were set to 600 / 1700.

When I did a PIV tune, it drove the motors to 42 which locked it up. I would have thought that a position tune should stop short of the limits set - given that they would be set for a reason.

Is this the intended behaviour?

Position Limits are only respected by the position commands. The Autotuner is not controlling position. It is using the minimum space and time it can to measure the motors capabilities so it can calculate proper PID values. Some setups will not have enough room for that. In that case you will have no choice but to manually tune the PID.