I read this on Steve Stafford's blog and wanted to spread the word. I have sent this to Autodesk as a support issue. I would recommend for you to do the same!
"Revit alters the lines in a imported cad file if they are very nearly horizontal or vertical. It has done this for quite some time. It isn't clear if it isn't a problem very often or if it isn't noticed very often. I'm reminded of this issue by a recent post at AUGI naturally.In this instance a member wrote that a property line (in a cad import) whose bearing is 89 degrees 57 minutes and 56 seconds is altered by Revit to simply 90 degrees even. The cad file isn't "changed" but what we see of it in Revit is."