Yes, i'm pretty sure, that we had this topic before - but i don't remember the correct search terms... If this is a model from 3dlabprint.com, disabling of "Union Overlapping Volumes" should be the way to go (it's in the "Mesh Fixes" group in Cura).   Basically their files are incorrect, but they don't care much... Here is a related discussion in the forum of 3dlabprint.com.
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