On one account, I had some extra DBG cash so I decided to "Finish Now" some quests. I'm 0/5 on successes (all failed) on the ones I finished using DBG cash. All of them had 80% or higher Success probability. TBH, the only reason I continued to spend coins was to test if it was broken. I'd rather not test any further with my currency (am only out maybe a hundred or so coins so no biggie).