One of these customizations is a simple function run when the document is first loaded that checks a couple attributes of the root note:
var actDoc = Application.activeDocument;
var docRoot = actDoc.getDocumentElement();
var rootName = " + docRoot.getTagName();
Right now, docRoot is returning null which breaks the getTagName() call. Other exceptions in some of our other custom ACL also say:
Wrapped com.arbortext.epic.AclException: [A12653] The "detail" command is illegal for a text file.