Attachment is a .brep file, and it contains only two faces. Try to stitch them using sew API (tol=0.01). After stitching, one edge's tolerance changed from 0.5 to 116. I have reproduced this problem in 6.3, 6.5.3 and 6.6.0. The raw two faces have no topological or geometrical error. I think I have reported the similar bugs two times ( including OCC MantisBT system), but on feedback at all. In fact, this .brep file is extracted from a large iges file, the stitching result is not good in raw file. Many topological or geometrical error happens after stitching.