"Doors opening at speed" isn't an issue for the car in general. How do we know that? Because very fast SL-Cs, like Sharkey's old car that now does 178 MPH in the half aren't doing that, because the original car that did a reported 194 MPH at Daytona didn't do it, because the later Raver car doesn't do it, the factory 01 race car didn't do it, and so forth.
But the one in the video clearly was, so there is something going on, obviously.
My guess is that it's something simple, most likely loose lower hinges. I don't think the door is actually warping- because none of the other cars are doing that. In other words, I doubt that this door is the only one that warps at speed. What seems most likely to me is that the door is actually somewhat loose in the opening. That could easily cause the door to misalign at speed like the one in the video. Even a door that seems to open and close easily could be loose at the lower hinge. And as the owners who have some miles on the car know, the hinge bolts sometimes work loose- you have to really tighten them down, and use Loctite to keep them in place. And if the car was built without stiffeners at the hinge, that probably aggravates the problem.
Another possibility is a loose pin where the door latches to the body. It takes some time to get the pin exactly in place, and if it isn't tightened correctly, using the right kind of washers and nuts, for example, if could allow the door to lift slightly open as seen in the video.
Whether the forces on the door are internal (pressure from an open roof vent) or external (negative pressure from air over the roof and door edge) doesn't matter much, IMO, as we know from experience with many cars at very high speeds that doors seem to stay sealed at speed, including those who have air ducted into the cockpit from an open roof vent.
That's why I think the most likely cause of this is a lower hinge that needs tightening. And/or a loose pin (or latch?) on the other end.
That's what I think, anyway.
