This is what happens: I select the roof where the red arrow points, and selects as shown in the first picture.
Then, I hit Esc and selects the roof at the end of the arrow in the picture below. Seems like it is two roofs, one big and one small, the small is overlapping the big. But its not. Somehow, when I select the roof on the picture above, I select both roofs. When I select like in the picture belov, I select only halfe the roof.
And here comes the interesting part: Somehow, when eksporting to IFC, the translator sees theese as two separate roofs, which means the small roof with the windows is exported twice. As you can see in the lowermost picture, there is an image taken from the Solibri-view, and the roof pointed by the green arrow looks like it is two elements occupying the same space.
I've tried almost every trick that I know of, no hidden layers, no double objects, nothing....
my guess is you have two roofs in the same plane, either entirely overlapping or a single smaller roof partially overlapping. Try "edit > check duplicates > select duplicates" and see if it somes up with any.
You could also use the element ID manager to give each roof a unique ID number, then find and select roofs by element ID to track down the overlapping roof... or just select the roof, then shift + drag select to deselect the roof and simultaneously select any duplicate/overlapping roof...
but in any case, yes, it appears you have duplicated roof elements.
BIM solutions and trouble shooting (self proclaimed) expert. Using Archicad 26 5002 US on Mac OS 11.5.2
Issue solved. It seems as if nested boolen operations was the problem, although I don't understand why. The smallest roof was the operator for cutting the walls to accomodate the roof. Done that 100 times. But somehow, when doing boolean operations on the second roof, and including the first roof, everything messed up. Don't know if this is a bug or whatever. Issue resolved, nevertheless!