In the attached file, the object - despite the fact that it is not well made and has open edges etc. - is not flagged as “bad”. However, its bounding box is erroneous, too big, despite the fact that all surfaces are shrunk. There is one planar surface (the “bottom edge”) that appears to be causing the problem, extract and delete that and all is OK.
BadBB.3dm (1.3 MB)