Lost Subscription Requests

We are using QuickFIX/J 1.5.2 . Our application runs as an Acceptor for our client. The client sends us a subscription requests for different symbols. However, out of 10 subscription requests send by the client our application gets only 8 requests. The 10 requests do show up on our fix messages logs. However, fromApp(quickfix.Message message, quickfix.SessionID sessionID) call back method only notifies us of 8 requests and not 10. Why fromApp() method notifies us only of 8 requests and not 10 despite of ten requests showing up in fix messages log? It happens sporadically. Our client is very unhappy about it and our reputation is on the line. Please, advise ASAP. Thanks.