I am the developer of a widely distributed application written in Delphi 5. Recently there have been some reports from users that when closing the app, it remains in the taskbar and can only be terminated using Task Manager. I have occasionally seen this myself and have also seen an instance where it wasn't in the taskbar but the process was still running, but I haven't found any specific action that causes it. This has only been happening for the last few months so I assume it has something to do with a recent code change, but I don't know exactly what causes this and have no idea how to search for the possible cause. I would appreciate any hints on what causes this and how to find the part of the code that needs fixing.