Error/Warning 'properties\dzenumproperty.cpp(734)'

I have a script loading some H.Materials and Materials files. My object (a book) has 2 Material Surfaces ('Cover' and 'Pages').

If I load an Iray Material (or H.Material) Preset, everything is fine:

Scene.setPrimarySelection(aMyBook.bookNode);
var oContentMgr = App.getContentMgr();
oContentMgr.openFile(localPath+"IrayCoverPresetFile.duf", true);
oContentMgr.openFile(localPath+"IrayPagesPresetFile.duf", true);

If I try to load a 3Delight Material (or H.Material) Preset:

Scene.setPrimarySelection(aMyBook.bookNode);
var oContentMgr = App.getContentMgr();
oContentMgr.openFile(localPath+"3DelightCoverPresetFile.duf", true);
oContentMgr.openFile(localPath+"3DelightPagesPresetFile.duf", true);

I get an Error/Warnig "properties\dzenumproperty.cpp(734): Index out of range in DzEnumProperty::getItem()" but the file is loaded correctly:

var bFileLoaded = oContentMgr.openFile(localPath+"3DelightPagesPresetFile.duf", true);
print("File loaded:" + bFileLoaded );

returns "true"!

I noticed that the second 'oContentMgr.openFile()' command throws the error/warnig, which reffers to the 2nd matterial surface (pages) of my object.

Does anyone has come across this problem and know any solution? Is it critical for the execution of the script, or can be overlooked?

Thanks in advance!