You all know what inattentional blindness is. When you search for specific type of problems you completely ignore everything else that is going on. Even when you believe that you do not, its part of being a human. What I have discovered is that it happens the other way as well.
People tend to stop testing a certain feature when they find one apparent problem with it. It seems to get ‘ticked off’ as done, thus neglecting to think about it more. They do go deep with that issue they find, trying to see how bad the problem is and could it be exploited to be really catastrophic. But they do not ignore it to find other problems with that feature(/field/option/function/whatever/thing). Thus missing other, possibly very big, issues.
And that’s a bad thing. We, testers, need to think also what other problems there could be. Making a too quick (and wrong) decision to stop testing, thinking that when the discovered bug gets fixed so will all other problems that relate to the feature. This is true only some of the time. Usually testers cannot make that judgment call as they do not know the code that well. There could be million reasons why stuff breaks, do not let it trick you into thinking that there is only one way.
Sure, when the developers say that stop looking into it, then fine, or if it is completely broken. Otherwise keep on drilling. Use the “sexy chick” heuristic. Be inventive.