Replace external PDF JobOptions

Hello, 

I work on Windows, and for my client I test on Mac and windows. 

I use importFile into a plugin for Indesign to get any pdfExportPresetFormat that a service send me.

It's ok, but when I recall that function to get an updated version of my pdfExportPresetFormat, I have a new one instead : 

- myPreset

- myPreset_1

- myPreset_2

...

I want to replace the first .jobOptions with a new one with the same name, so : 

function importPresetFile(filepath, name) {
    if (app.pdfExportPresets.item(name) != null) {
        app.pdfExportPresets.item(name).remove();
    }
    app.importFile(ExportPresetFormat.pdfExportPresetsFormat, filepath);
}

Sometimes it works, but sometimes the right to delete is not acquired, and I can just import the same document at the end of the list.

I checked this forum and the doc, maybe I am missing something, please help me.

Tanks in advance.