I have the suspicion that many bug-fixes carried out by our developers sooner or later cause another bug, simply because the product is too complex.
I'd like to improve the quality of bug-fixes, i.e. make sure bug-fixes do not produce additional errors in the code. For that, I'd like to be able to measure how the quality changes as I apply various counter measures.
Is it a good idea to instruct bug-fixers to always look for the cause of their defect, and then evaluate the ratio of previous bug-fixes being such cause? I'm hesitant about this due to the obvious higher expenses and unwillingness of developers to blame themselves or fellow colleagues.
Is there a better approach?