Packet loss through VPN up

Hello,

I have two sites connected, FGT-90E(Site N°1) and FGT-60E(Site N°2).

I got a VPN tunnel between both sites, my objective is to connect computers from Site N°2 on a server from Site N°1.

But i've got a problem, indeed, when computers are connected on the server, there are disconnections.

I did some tests to find the cause of my problem:

First i did a ping from my UTM Fortigate on Site N°1 to reach Internet, there was no problems.

I did the same thing on the UTM on Site N°2, same results (OK).

Finally, i did a ping from a computer on Site N°2 to reach my server and there are some packets loss randomly (continious ping during one minutes @20-100ms and message "Request timed out").

VPN is always UP into Fortinet "VPN Monitor", and I don't know how to check for errors. Network on the computer on site N°2 doesn't show any message (connection errors).

I have some equipements connected to this VPN, that use software, and that packet loss seems to disconnected this software.

- Do you think these packets loss could be the origin of the software error ?

- Is there a solution to resolve this problem ? (commands line through CLI console to analyse these errors)

Thank you in advance for your help.

Best regards,

- John -