WheeledVehicleSpring Problem

Hi all
I am developing a game in TGE 1.5, it is kind of car racing games, with some AI Vehicles on the roads.

when adding AI vehicles there is a problem. When i disconnect, it just closes the entire application without going to main menu.
I debugged through script and found that there is some problem with WheeledVehicleSpring datablock.

here is the code for it

length = 0.85; // Suspension travel
force = 3000; // Spring force
damping = 600; // Spring damping
antiSwayForce = 3; // Lateral anti-sway force

when i decrease the force attribute to 1000, it works correctly and the application itself does not closes.
But now problem is, the vehicle's tires get into the ground.

Anyone have any idea what i might do.

Thanks in advance