Hi,

Be careful when you want to improve multipolygons : tags should be on the relation, not on the outer or inner ways, see "Example of tagging for actual features" here = https://wiki.openstreetmap.org/wiki/Relation:multipolygon#One_outer_and_one_inner_ring

I fixed the 3 wrong multipolygons : https://www.openstreetmap.org/changeset/135556021

Best regards