Instead of shooting the truck I normally throw something random from my inventory at it. Usually a rag, this also engages the physics and causes it to fly about, once settled it is safe to get in. I assume randomspawn that your truck will be out of the texture by Sunday. Server restarts cause trucks to "fix" themselves. This sometimes takes a couple restarts if the truck is stuck good, but usually one restart works. If not the bullet trick should work.