Intersecting inner is ignored

[nlehuby]

This part of admin is an enclave : https://www.openstreetmap.org/way/137109677
It is part of the city Pieve del Cairo, whereas it is fully inside the city of Isola Sant'Antonio.

In Cosmogony, the enclave is is both cities 👎
This may be because the enclave shares one point (one node) with one of the city boundary.

[amatissart]

This is indeed due to a bug in how inner boundaries are associated to outer ones when building multipolygons in osm_boundaries_utils.

Here is the fix I suggest: Qwant/osm_boundaries_utils_rs#6