It seems the longer cable for the Raspicam wasn’t the problem. I bought two new cables 30 and 50cm long. The 50cm cable arrived with multiple dents and bends, so I used the 30cm cable. And voila, the Raspicam is NOT being detected.
It only works with the original 15cm cable. I tried all cables, checked the connectors for dirt, did rpi-update, no luck.
Now that I think of it, I remember it stopped working in my Wildthumper Rover with the longer cable some time ago.
Did anybody have such a problem?
Since it works with the short cable, I suspect something is actually broken on the camera module, which kicks the voltage/signal out of specs, with the longer cables.