Race condition in GroupRequest can make it wait for the full timeout even after all responses are received.

GroupRequest.execute broadcasts the request, sets "done=false", then waits for a reply.
If all the replies come in before it sets done=false, it will overwrite the done=true set by the responses and wait for the full timeout, and then return false.

Note that the internal uses by MessageDispatcher/etc do not check the return value from execute, so this does not affect the data returned, only how long the call blocks for.