Anomaly file "user_likesRatingScheme"

Hi all!
I'm using Alfresco Community 4.2.c and i'm incurring in something really strange.
I've put in place a customization and it works from almost 2 years. Yesterday I've created an Alfresco user "dave" and some services and rules doesn't work anymore.
The error in the logs was "NullPointerException" for the same piece of code used both for rules and services to retrieve the nodeRef of a particular folder "myFolderRep":

		List<ChildAssociationRef> childList = nodeService.getChildAssocs(docLibrary);
for(ChildAssociationRef s : childList){

			NodeRef childRef = s.getChildRef();

			FileInfo childInfo = fileFolderService.getFileInfo(childRef);
if(childInfo.getName().equals(myFolderRep)){<-- here NullPointer

				repositoryNodeRef = childInfo.getNodeRef();
}
}

After some hours of troubleshooting i find a file named "dave_likesRatingScheme" through Alfresco's NodeBrowser that resides under the docLibrary, at the same level of the myFolderRep folder. It was an hidden file not visible by Share or Explorer navigating the repository.
Simply deleting that file i solved all the issues.

Someone knows which type of file is that? Maybe it is related with user preferences such as favorites and likes but why i have never seen a similiar file for the other user i've created?? and how it is possible Alfresco API have an error retrieving info of that file?