Greg has a very strong point here. RJ45 connectors, while normally reliable, can become fairly unreliable. Many factors can contribute to this issue. This is a big issue on my team. We have managed to damage beyond repair a few laptop's Ethernet ports.
The repeated connecting and disconnecting that takes place with most Driver's Station laptops can easily contribute to their early demise. There are a couple things that can be done to help reduce this wear and tear. One of the simplest and easiest ways to do this is to use an
Ethernet Port Saver. Install it and tie it down so the end attached to the laptop doesn't move WRT the laptop.
Another issue I have personally seen giving lots of teams grief, and may apply to this thread directly, has to do with the design of the Ethernet port on the laptop used for the Driver's Station. This design can easily cause intermittent connection failures as well as the cable completely coming out of the laptop.
Here are a couple pictures of my personal laptop that has been used as a Driver's Station and has also completely lost the cable when bumped just a slight bit. This is an Acer laptop, but I have seen this same configuration on several different manufacturer's laptops.
In the second picture I am pulling down on the small cover plate that opens up when the cable is inserted. This cover rests right on the latch clip for the cable. Any pressure on the cover causes the cable latch to release. Believe me, it happens A LOT!!
The resolution to this is to make a relief notch in the Driver's Console assembly so that no contact with the cover plate can be made unintentionally.