It is all guess work by the JAIC as they announced all of this (17 October 1994) before the bow visor had even been found (18 October 1994). There is no evidence anyone saw the bow visor or the ramp fall off or open and nor is there any evidence that the car deck was flooded as a cause of the accident. The JAIC are going by the word of third engineer Treu, who claimed to have seen water entering the ramp at 1:15 on his monitor in the engine room.and before the vessel started to list and AB Seaman Linde, the fire patrolman, who kept changing his story. He told Dagens Nyheter 7 October he was on the bridge and was then sent down to inspect the car deck because of water on inside the area. He told the commission he was on the bridge with different persons and this time he was sent down to check the noise.
Instead of waiting to examine the bow visor and carry out a proper investigation, the JAIC already decided to run with the observations of two or three of the crew. Whilst eyewitness accounts are invaluable, an eyewitness can't necessarily determine the cause of an accident if it is based on intricate technical faults such as weak mechanics.
It decided that the car ramp was open by 10° leaving a gap of about a metre and too small for them to send in their ROV's. They didn't really test their own hypotheses. It is hard to see how water flooded in through this relatively small gap to an area 5m high to sink the ship so quickly.
Hmmmmm..... I wonder:
The bow visor was missing from the wreck of the ship when it was surveyed on the seabed. The bow visor was also nowhere remotely near to the wreck on the seabed. The bow visor is/was incapable of having been moved (or of getting up and moving under its own steam) so far from the wreck. If the bow visor had been properly closed and locked at the time the ship sank, it would have remained attached to the ship and would still be attached to the wreck on the seabed.
Therefore: the bow visor
must have come detached from the wreck
before the ship sank. That's Part 1.
Part 2: when the wreck was officially surveyed, there was visible damage to the part of the bottom lock (for the bow visor) that was attached to the hull of the ship. And there was also visible damage to the top hinges and the hydraulic piston mountings. And there was also visible damage to the area of the hull against which the bottom of the bow visor would ordinarily have mated.
Therefore 2: the bow visor must have detached from the ship because its bottom lock failed, causing it to swing up and down by its top hinges (banging down each time against that mating surface on the hull) until eventually the top hinges and pistons failed in turn - at which point the bow visor no longer had anything attaching it to the ship and it ripped free, sinking separately some distance away.
Part 3: the bow ramp, as viewed when the wreck was officially surveyed, was visibly deformed. And this - coupled with what the investigators knew about a) the operational interactions/interference between the bow visor and the bow ramp and b) the fact that they knew by then that the bow visor had failed and totally detached from the ship before it sank - mean that.....
Therefore 3: the loss of the bow visor and the deformation to the bow ramp meant that the bow was no longer watertight at these points, and that the vehicle deck of the ship
must have been exposed to open seas prior to the ship sinking.
Part 4: knowing all of the above, and knowing the sea conditions on the night of the sinking, and knowing the appropriately-weighted sum of witness testimony, and knowing the likely rate of seawater ingress through the broken bow door section, and knowing the mass of seawater on the vehicle deck that would cause the ship to become terminally unstable and non-buoyant....
Therefore 4: the ship sank because the bottom lock on the bow visor failed; causing the bow visor to swing up and down in the ocean swells until its other fastenings failed as well; causing it to detach completely from the ship; causing the bow ramp to become dislodged and deformed; causing the vehicle deck to become open at the bow to the oncoming seawater; causing seawater to rush in at rapid volume/mass into the vehicle deck; causing the ship to experience a terminal loss of stability and buoyancy; causing the ship to capsize and sink.
Let me know if you'd require any further clarification.