We have a VIP on our BigIP that sees a lot of connections. The TCP profile applied to the VIP is TCP Progressive with no Nagle. What we are seeing is after a very small amount of data the Window size on the F5 Self IP to Server connection is going to zero. The back-end server is able to maintain its buffer levels. The intention of applying a progressive profile was to take care of varying conditions and connections. We saw over 600 TCP Zero Window instance from the F5 to the server. all being sent by the F5. I am not sure what tweaks to the TCP profile i need to do to solve this problem.
Take a look on this two links below, it can be useful for debug you TCP zero Windows issue.