Will this not Help?
LOOKUP(SUM([# of Problems]),0) –LOOKUP(SUM([# of Problems]),-1)
Or You may use Quick calculation to Find Difference from Previous
I've tried that, but it doesn't work because it cancels out all the instances of problem counts going up, then back down again, instead of adding them both together.
What I need is the difference calculation performed first (at the row/item level), then the absolute value operation (to prevent the cancelling-out issue), then the aggregation.