When sufficiently large ID numbers are used by the GLM loader for internal object reference, the correspondingly large lookup table cannot be used properly. The solution is to use a non-array data structure of some fashion to store the objects with their load-time ID number. Constructing arrays with hundreds of thousands elements for some two hundred objects is simply inefficient.
Might this have been handled by the hash table additions by Ausgrid folks? It's a pretty old ticket...does it even have relevance anymore?