While there is a great deal of care taken in WIMWI regarding the grading procedure (understandable given the extent of importance acads and your CGPA carry) there still exists some amount of randomness in it.
Exams are graded in quite a random way sometimes, you write something thinking that is the answer only to be told something 'more' was expected. If you say that the question does not ask for that analysis, you are told that is the way the professor wants it.
Assignments are declared to be presentations and written reports are demanded with unbelievably tight deadlines. Component weightages are changed and flexed in a way that to the naked student eye seem arbitrary.
I take this in my stride saying this is another way of training us for the big, bad world out there which has no intention of being fair. WIMWI has found a way to fool us by randomness.