Ooops I found a disturbing issue...
I have seen that the original strings are removed from one xul file BUT NOT replaced with the newly created entities. More surprising, the new entity is duly reported in the dtd file with the corresponding strings
Here I attach the original xul file, then the processed one (with missing values and labels!) and the resulting dtd.
 I think the issue occurs each time I change the entity name in the editing dialog before launching the process (I will check that)
[edit2] I checked and unfortunately it trims again some labels and values even if I did not change the entities' names
[edit3] for information the same test file is correctly externalized with the previous version, so it is obviously an issue related to the new code part.
Gulp!! I've tested and works fine
I use these configuration files [attachmentid=2239]
Here the resulting files [attachmentid=2240]
I make some other test...