I work in software development and have worked on two projects with the same piece of software being used in both, but each are slightly different. The second was built off the first's code with functionality changed a little.
The software is an add-on running in the background for another software application. The first project's version didn't crash when the main application was closed. The second project's version crashes every time the main application is closed, and causes the whole system to hang for 30-60 seconds, a serious problem. I know the crash behavior is not correct: one, being a software developer I know this is obviously wrong; and two, the first project's version didn't have the problem.
The first and second project versions of the software have been developed by two different developers. I have tried talking to the second project's developer several times about the issue, but they have come back basically saying it's not a problem and that we should find a way around it, like creating a special button to close the add-on running in the background before clicking another button to close the main application.
I don't understand why they don't see the problem as I do. This developer is a manager level developer above me. How do I go about explaining it to them? I was hoping someone else would have noticed it by now as we have demoed the software once already to a prospective client. I thought about talking to my manager about it. I also considered talking to the project lead about it and seeing if he'll look at the problem and "notice" it and talk to us developers about fixing it.
How do I handle this in the most professional way? I do not want to create an "atmosphere" in my office or change any of the relationships I have. I have worked with this developer for a year now and will probably be working with them for the foreseeable future, but that doesn't matter as I don't want any relationship to change whatever I do.