BF70x USB EP0 sent stall bit.

I have a problem regarding a USB implementation on a BF700 blackfin EP0 control transfer line.

Enumeration of a USB to Serial works fine, as do serial communication.

However once in a while, a set baudrate control transfer fails.

Looking at a USB analyzer, I can see the blackfin sends a STALL in reply to the comport settings.

The bit USB_EP0_CSR[n]_P.SENTSTALL has been set, and looking in the manual (Stalls Issued to Control Transfers), it tells the blackfin has send this stall because it did not like the host transfer.

Now I have made a small program that continuously changes the com baudrate, and after a while the stall is send.

I use the USB analyzer to look for differences between all the changes that was successfully and the last one that fails.

None are visible...

Help is appreciated :)

Best regards