Why does the tilt pin have a big force when launch just begins?

I have conducted a launch analysis with MOSES. then I use the command LWFORCE  to explore the reaction force during the launch.

I found that the pin force is not equal to 0 when event =0. Actually it is a big number. But obviously the jacket  is not on the rocker when launch just begins.

MAY YOU HELP ME TO FIGURE OUT WHY THAT HAPPENS?