Have you overcome this issue or are you still working on this?
If you're still working on this issue, please let us know the following information
Are using auto or manual slave FIFO mode?
What is ur endpoint configuration i.e. EP2 quad buffered, EP6 double buffered etc etc
The flag information (which flag is what and whether they're behaving as expected i.e. say even if data doesn't change doesn't clocking out all the data does the FLAG indicate the buffer is empty etc)