You're right. You won't see the crane move when loading cargo because it doesn't. At the start of a job they will position in line with the hold they are loading/unloading. The crane will drop the gear, which hook onto the top of the container and then lift the container off the chassis and it will move towards the ship and set the container into the hold. Then the reverse for off loading. The crane itself does not move, and this video is not clear.
You're right. You won't see the crane move when loading cargo because it doesn't. At the start of a job they will position in line with the hold they are loading/unloading. The crane will drop the gear, which hook onto the top of the container and then lift the container off the chassis and it will move towards the ship and set the container into the hold. Then the reverse for off loading. The crane itself does not move, and this video is not clear.
There has to be some video on this... Here is a link to a bunch of nice information on gantry cranes. https://www.marineinsight.com/ports/container-gantry-crane-construction-and-operation/