Why does my vehicle change gear without input when begin play

Hello! I have a problem about vehicle.

I’am trying to make a rts project. I have made a vehicle blueprint and this project allow spawn vehicle after game playing.

It work well when I only spawn one vehicle, but once I spawn more than one, it begin worry. For example, spawn two vehicle, I found that the second one change its gear On-going. And I didn’t konw how to solve this problem.

Does anyone can do me a fever?Thank you.

Can you show the BP for changing gear?