What could be cause of application only working 10% of the times??

I'm working with a legacy application , it uses java with hibernate and a flex front end application. it recieves orders which should be put in the database.
I thought the application was completely broken, however when i arrived on work this monday i saw it processed 2 orders. Looking at the backup system, it turns out we had 20 orders.

Anyone have any suggestions how it could be possible for an app like this to only work 10% of the times?
I dont know enough about BlazeDS to fix it without any pointers, all ideas are appreciated.

Thanks for your time.
Bart

EDIT: I've ruled out errors in the flex application, as it sends the proper values to the java app. The logic of the java app seems okay too.
I'm getting the feeling that sessions may not be created / closed properly, i believe the application uses spring/hibernate which should manage that, i believe.

the app runs on tomcat server. The hibernate statements are not executed, but when i look in tomcat app manager i see the session is still open

When i use fiddler, i see 504 error on my "messagebroker" session

EDIT : pfff the flex application contained an unreachable if statement, it was making the connection, just not sending data. everything is working perfect now :P

The issue that you mention is too specific to the application and there's no way we could help with this without knowing more about the technical details about the application. You'll have to first try and narrow down the issue to a specific area. Usually looking at the logs can give you a hint on what might be wrong.