A black and purple chequer board effect means you do not have the correct textures in your loaded libraries.
Check that you have the correct libraries loaded in Archicad.
Check the Library loading Report - that will tell you what is missing.
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Have you somehow managed to duplicate your Archicad model?
i.e. two of everything in the same space?
No, its more that all the columns inside the walls and roof rafters are showing through the wall they are in.
And unfortunatelly they were already modeled this way and had no issues before. Maybe my model got corrupted somehow.
Will likely just work from an older backup and re-work from there. Thanks for your help though!
It sounds like you have a situation where the columns and/or beams are modeled such that their surfaces overlap with the wall's (or roof's) outer surface and they "occupy the same space" (or exposed surface area)
Which is fine except the BIMx program (and indeed most 3D programs) don't know how to intepret a situation where two or more surfaces overlap and occupy the same area. And so it tries to translate that by showing both surfaces at the same time, hence the flickering as it switches from one to the other.
(*and to be honest, the program is correct in the sense that this is wrong since in reality this isn't how it would occur in real life. Normally the Column would end up getting furred by the wall's finish (or roof's or ceiling finish) and for the side of the column that meets the wall, there wouldn't be any outer furring or finish and instead they'd share the wall's finish).
You could try one of two things (one of which I don't believe will work so you might have to be smart about it.
1) the flickering is an indication that the two objects causing the bug have different surface materials and the program is trying to show both. So you could try to make both the column and the wall the same material finish. This is just based on the fact that we know that ArchiCAD cleans up when you have two objects that share the same material to show them as a unified single finish instead of that flickering effect.
The question is whether BIMx will do the same - my assumption or theory is that since ArchiCAD is the one doing the exporting, it will export what it shows in its 3D window including any "clean-up" it does.
I'm not entirely confident this option will work because BIMx might be running a different algorithm to display what it receives from ArchiCAD and not do the clean-up itself.
In which case......
2)be a little bit more smarter or cunning in your modeling and manually do the "clean-up" yourself by adding a bit of separation between the column's outer face and the wall's (or roof's/ceiling's) exposed face so that they don't overlap.
Either by moving it slightly inside or if it's supposed to fit perfectly inside the wall then give it a slightly smaller (as in a couple of millimeters or fraction of inches, depending on your unit, small) total width or finish thickness.
This one will definitely work since it completely hides the column inside the wall and there's no overlapping to worry about. But admittedly it might take a bit more work.
All of this is assuming I understood your question correctly.
If not let me know.