We are AIX 5.1 QDX 5.3 r3 with no issues.
However, I’ve seen this when the server is in a remote facility where the response turn around is > 30 ms.
Might also check to see how many routetest processes are running. We found one case were the tool was exited incorrectly and the processes was not terminated. This was 3.8.1 – haven’t tried it in 5.3.
