Hi, doris.at is the official geo-data portal of the Upper-Austrian goverment, which includes the official data of the regional cadastre and land-registry. Especially the southern part of the current OSM area is not correct now. Normally it would follow the municipal boundary/border of Engerwitzdorf in this section. 

At data.gv.at there is also a municipal map of Engerwitzdorf where the area is differently marked than in OSM.
Just look at "Truppenübungsplatz Treffling" at the data.gv.at pdf-link: https://www.data.gv.at/katalog/dataset/ef524203-0a5b-4e57-88d6-01adae094d21/resource/fb1f705f-7df8-457c-9f08-23b9c8507b48/download/ortsplan.pdf
