I believe those could all be explained by a roll of the dice. Sometimes the dice fall where they are expected to, and the numbers on the character sheet produce more-or-less the results expected. However -even in systems with a bell curve- I've seen the dice go on a hot or cold streak for someone.
There is also the 'human element.' Sometimes, somebody does something which seems at odds with what is logical given the situation. Sometimes, this leads to die rolls which wouldn't otherwise need to be made. Whether that leads to success or failure, the fact is that that element of choice -the human element- created a situation which wouldn't have been there otherwise.
Then, in some circumstances, those two things happen at the same time.
In the abstraction, this seems a reasonable interpretation of the model and its inputs (minus the fact that the math doesn't match up - which is rather important to a simulation if it is to have any fidelity to reality or the phenomena it is attempting to model). However, I would include a third, and equally as important, input that is firmly outside the internal locus of control of the character:
Entropy and its proliferation.
This could be your gorge (either the inception of the entropy or its proliferation), if you wish it.
Of course, again, this all presupposes that:
1) Your design aim is to model the micro-phenomena, and its accompanying minutiae, at play.
2) That you're willing to disregard the staggering lack of fidelity to the phenomena you're modeling due to the dubious math and the numerous built-in kludges/abstractions in the system (but you're somehow able to take a hard line on mechanics working outside of the model, skill challenges, due to their lack of interfacing with the (already) infidelity of your kludged simulation?).
I, and many others, do not care for 1 or 2 within our games (or at least within the framework of our out of combat scene resolution mechanics).