Well, I told you: it's the decision function 
SUM is definitively not messing with these or any other parameters.
And no, there is no way to track back who changed the parameters.
Since I've seen customers running with similar manual setting, I would suspect that these come from some "best practice" document of sorts that is floating around in the consulting space.
However, the recommendation for these parameters always had been: use the default or better know well what you are doing.
Just set the parameters back and you should be fine.
And don't forget to turn off the trace again.
- Lars