[Serusers] Ser sends messages not in that order in which it has received

Hi, We have found one unpleasant situation with a Ser often shown at greater loadings. At greater loadings and at work of a Ser with number of child processes greater than one (Parameter 'children' in ser.cfg), Ser sends messages not in that order in which it has received. And as the result appears request pending errors. We simulated this situation continuously reinviting the remote UA. Usually the error is occured on the tenth-twentieth reinvite. In the attachment there are SIP logs reproducing this situation. Somebody can tell in occasion of this problem, or offer the decision? Or whether there is a version in which there is no this lack? Alexandr