It is hard to tell what's going on without looking at the XML. Is ACCOUNT within MEMBER, or vice-versa? twig_roots would not like that.

BTW, Do you really need to use twig_roots? It seems that generally, users tend to use it in cases where it is not needed. In your case, you should probably only use it if ACCOUNT and MEMBER make up just a small part of the entire XML flow, and you don't want to load the rest of the document. If your XML is mostly a list of ACCOUNT and MEMBER, then there is no need to use twig_roots. Even if it is appropriate in your case, I hope that others will read this warning and think twice before using twig_roots ;--)