Hello gilberti,
Thank you for your post.
I reproduced the error. It will be fixed in future versions and I'll post here about the update.
Meanwhile, to avoid incorrect naming please do the following:
-Select necessary intervals
-Push the "Save" button
-In the "Save As" dialog mark the following options:
"Use mask for output files"
"Save keep fragments separately" or "Save cut fragments separately", or both, if you need to save all fragments.
-Push "Save" and you'll get the output fragments with the correct naming.