you have both modern computer components and older control units, using higher voltage controls.

This mix makes it dangerous because anything can set them off. Especially if the magnetized tool attracts another loose screw, bolt, or mechanism that is part of the control set.

It can set the controls to a dangerous condition, that can lead to disaster after energizing the circuit for testing. Using them with a hot circuit could be fatal.

Newer units have safety built in, so it is not so much a factor, but real world factories are still using units designed in the 1930s(some actually built in the '30s) and still operate to this day.

Whenever possible we modified them to take more modern low voltage computer control, but this only goes so far, as it is still expensive to get high voltage diodes, transistors, and similar IC components built to scale.