Do you actually want to intersect the polygons or just find the overlaps?

At the moment the polygons A,1&2 are sent into the area on area overlayer. One area is returned which is the area of polygon A which does not overlap any other polygon. The other area that is returned is the area of polygon A which overlaps both polygon 1 &2 (hence why overlaps says 3)

This is the shape returned where the poly2_ID is missing, it is the area that is not overlapped by any other polygon

If you are just looking for a report of which poly2_IDs overlap poly_ID A then I'd suggest a spatial relator set to intersect, build a list then list explode.

Looks like you have a self intersecting polygon. It's a bow tie in the data.

If you add an AreaGapAndOverlapCleaner before the overlay and group by fme_feature_type it will repair the geometry and output the correct result.

Example of what a repair does.

Hello,

I have checked the geometry and I don't see bow tie. But I have 2 completely overlapping polygons.

I have misinterpreted how AreaOnAreaOverlayer works.

Thank you for your help!

In the SpatialRelator ensure that you are building a list of all related IDs

Then use the ListExploder Transformer to explode this list and you will then have a record for each related candidate

Thank you again and sorry for taking your time. I just figure it out by myself and deleted the question probably at the same time as you were typing your answer. My mistake was that I was using list builder instead of building list from inside the spatialrelator...

Thanks again!