Hi Haiyang,
Thanks for using the forums!
What I am getting from your question is that you are seeing packet loss early in your route (up to your firewall) when you are tracing 5 targets, but when you close all but one target the packet loss goes away. Did I get close to what you are asking?
Either way, it is very tough to tell what may be going on here without being able to see any data. If possible - would you be able to send over some screen shots, and perhaps a .pp2 file (by clicking "File" -> "Export Sample Set..." and then attaching that file to an email)? You can email this to support@pingplotter.com.
If you could do this, we would be more than happy to take a look at the data and let you know what we see happening.
If you should find yourself with any other questions, or needing any other assistance - please don't hesitate to let us know also by emailing us at the email address above.
We look forward to this email.
Cheers!
-Phillip