I have a Skyline roof on my LWB T6 and the roof has now opened TWICE on the motorway, much to my wife and kid's terror. In fact she'll no longer drive the van.
Both times there's been a very loud bang, as the cam at the front detaches from the locking bar, and I've had to make a crazy swerve to reach the hard shoulder. As I slowed down and pulled over the cams seemed to release on both sides and roof completely rose. If it wasn't so terrifying, it would almost be comical - people gawping at us, wondering why this mad family are pulling over to camp on the hard shoulder.
To your points: I'm fastidious about the way I lock the cams, particularly after the first incident. I ensure they're fully engaged, and check the roof is firmly pressed down. I then get someone else to check it. Even with that, these failures have happened. Secondly, on both occasions, the cam bar has been bent upwards at 45 degrees indicating that it's engaged, but somehow under tremendous pressure.
The first time it happened we were - completely by chance - near the Skyline factory in the West Country. They replaced the cam free of charge, but it was clear their line was that these failures were user error. Yesterday my roof opened again, this time at 65 mph on the M6, and I had to drive the 80 miles home with a strap tied between the roof handle and my front seat. Once again the cam bar is bent.
To the point made by Grim Reaper, the overlap of the cam bar and roof latch seems a critical aspect of the design. I'm puzzled why there is no hook of some sort on the end of that bar to literally hook on to the catch.
In my case the roof has clearly lifted at high speed, bending up the cam bar, before it reaches a critical point where it slips out of the latch causing these high-speed openings. My converter is going to replace the cam this time, but I think I will have to find a way of physically strapping the roof down in future.
Finally, wherever the fault lies, it strikes me there should be something in the design and/or installation instructions that completely negates the risk of this happening, another visual layer of security. There is no back-up if one of those cams opens at high speed, and trust me, it's not a pleasant experience.