Traffic going through fortigate unstable often timeout, but not when bypassed from fortigate

[fiesta]

Hi,

Good day to you.

User experiencing unstable connection while going through fortigate but when bypassed from fortigate traffic is fine.

And I see many this info in wireshark between client and server or server to client when traffic going through fortigate in tcp stream.

[This frame is a (suspected) out-of-order segment]

[Previous segment(s) not captured (common at capture start)]

[This frame is a (suspected) retransmission]

Is this a potentially asymmetric or something else?

Client said there have tried to bypass UTM and all service port but still having timeout/unstable issue.

Thank you.
FW.

[fiesta]

any traffic shaper along the way to server? or try using different interface from client <> fortigate

[azmadhussain]

Below action tried

1. Traffic shaper apply then remove
2. policy route applies to specific router IP 
3. tcp mss size apply
4. NP offload 

          edit 1
          set auto-asic-offload disable 

[fiesta]

Maybe try bypassing all security profile? try direct on fortigate (client (iperf client) <> fortigate <> client (iperf server)) on the same/different interface? restart? upgrade os?