Openframeworks Essentials chapter 3 issues

hey, i been following the book openFramework Essentials and i been having a problem with the xml loading and saving preset from chapter 3, sometimes when i save the xml the console show this
[ error ] ofXml: loadFromBuffer(): DOM ERROR
and the app still works
but when i try to load the xml files preset the app gui doesn’t work anymore
i try with the files from the book but they don’t work either.
did someone had the same issue?
how can i fix it