If any of the stairs are damaged and cannot stay attached correctly, there is a chance of falling into the machinery below, which will not stop just because a human is in the way.
If the failure is in the braking system, it can quickly turn into rapidly moving stairs, which can be very lethal.
Most escalators have multiple independent braking systems so that this doesn’t happen, but some poorly maintained escalators have been discovered with 2 or even all 3 systems disabled.
Why?
If any of the stairs are damaged and cannot stay attached correctly, there is a chance of falling into the machinery below, which will not stop just because a human is in the way.
If the failure is in the braking system, it can quickly turn into rapidly moving stairs, which can be very lethal.
Most escalators have multiple independent braking systems so that this doesn’t happen, but some poorly maintained escalators have been discovered with 2 or even all 3 systems disabled.