6.5.1 incorrectly computes a shaded representation of the attached model, which was OK in 6.5.0 (but had similar issues in 6.4.2).
I already sent this model to the OCC team last March but apparently it was not added into the test database. Doing this again to get the bug registered in the bug tracker.
restore PFS04041r1.brep p
vsetdispmode p 1
See two screenshots made in 6.5.0 and 6.5.1.