I agree with Beagle on the opinion of quality of Heki... I wrote a critical opinion of them in
THIS TOPIC.I had one of the black colored "forks" of the rotating portion break off on my last camper... Crazy Glue did not work. But the rotating part in my situation and the "lug" as you call it are only part of a lock of sorts. I say lock because I am not sure if it is meant to keep the skylight in place while traveling down the road.
You mention that you "rope" yours down, but I just left my as is because there was a significant amount of downward force from the pistons holding it down. I installed new piston because the original ones would not hold the skylight in the UP position. I never worried about trying to get a permanent fix because they really held the window very well in the down position.
But, if you want to fix yours, the frame is relatively easy to take down for a possible fix. Maybe you can install a metal angle with small nuts and bolts to replicate the piece that broke. I had to disassemble mine because the shade slipped out of its guide track slot.
If you choose to take the frame down and the shade works properly for you, DO NOT LET THE SHADE SPRING AND ROLLER COME OUT OF ITS POSITION. It is similar to spring loaded roller shades on a house window in that you need to pre-load the spring. It can be done on the Heli but it is a PIA,