Its not that hard perse, but finding where the error is the harder part. The file is actually a very simple XML file.
If you have a title that the menu does works open up VPLST000.XPL in a text editor (Notepad is my choice) and then open of the VPLST000.XPL in a title that the menu does not work.
Compare them both and find where they are different. Using some trial&error editing you can make the menus work. Its not the same in every disk so I can't tell you "fix this and it will work". But most will work while playing with the different options.
There are some disks that require some heavy editing so make sure you save your original VPLST000.XPL files somewhere safe.