The following cut operation returns a wrong result in OCCT 6.5.3: only one face is returned.
The result is correct in OCCT 6.5.2: two faces are returned.
restore blower1.brep b
bop b_1 b_2
Can you reproduce the problem?
It is noticable that the cut-operation is slower in 6.5.3.
This is also my general impression. Do you know why?