Car SMBv1 Application Server Issues

Dear Guys, I need your suggestions related to the weird issue on a Fortigate Firewall which is related to an SMBv2 Application. As the Fortigate FW, Client and the Server lie in a single network and also I would say in a single subnet. Fortigate is running in a NAT-mode, also I have created a Virtual Wire Pair with the two interfaces whereas port15 is connected to a to Client and port 16 which is connected to a L3 Switch(MPLS Provider) where the Application Server resides. Its a sort of a Car Application, that check the employees and revert the daily results of the working hours. However, with Fortiagte once I have login the application and trying to access through the Client it doesn't show anything only reverts with a blank page. I have been stuck in this issue for 2 weeks. Even though I have been in contact with FortiTAC Support but they said Fortigate is working fine and there is a problem with the Application seems to be something on it after seeing the Packet Capture. Whenever I tried to bypass the Fortigate the Application works and shows me the Output. Note: I have created a bidirectional Policy but nothing works. I have tried to increase the session-ttl timeout, set tcp-timeout rst, set tcp-mss-receiver and sender on the Policy, set the MTU on the Router interface. Though the Client and Server send the RST Packets. Changed the DNS of the FGT to the Internal DNS nothing happened. Though tried every possibility but nothing worked at all. The firmware version of the Firewall is 6.0.10 as TAC Support recommends me to do that. UTM Profiles are also disabled on the Policy and also on the Feature Visibility. Any help would be appreciated.