Hi,

This forest multipolygon,  see https://www.openstreetmap.org/relation/4218385/history , needs a serious cleanup, inner areas that are no longer inner and inner areas that share a side which should have a single inner combo line drawn around them. 

OSM Inspector shows this picture at the moment
https://tools.geofabrik.de/osmi/?view=areas&lon=12.41508&lat=47.01959&zoom=16&baselayer=Geofabrik%20Standard&opacity=0.65&overlays=duplicate_node%2Csingle_node_in_way%2Cduplicate_segment%2Cway_in_multiple_rings%2Cintersection%2Cintersecting_segments%2Cring_not_closed%2Crole_should_be_inner%2Crole_should_be_outer%2Cinner_with_same_tags%2Cways

The dark blue is where inner is passing at least twice also flagged with duplicate segments. The light blue indicates an inner should be outer as well.

If you leave this area alone for the next 24 hours, I'll try to correct all the flagged problems, the net being that this forest is going to turn into 3 or 4 outer forest areas in a single multipolygon relation.

The Inspector view will update tonight sometime after 22:30

cheers