Modding Help Piercing projectiles stopping in place on first hit

So, I'm trying to make a weapon with projectiles that bounce around the terrain and pierce enemies on hit. However, they currently have an unfortunate tendency to stick in place after hitting an enemy the first time, which means they end up hitting slow enemies as fast as their invulnerability frames will let them. I am stumped about what's causing this, since I've changed the physics type of the projectile several times and tried adjusting the number of bounces. Does anyone see what's wrong with this code?

Code:

{
  "projectileName" : "magentaglobestandardized",
  "physics" : "bullet",
  "bounces" : -1,
  "speed" : 25,
  "timeToLive" : 3,
  "piercing" : true,
  "damageKindImage" : "icon.png",
  "lightColor" : [255, 10, 10],
  "image" : "magentaglobe.png",
  "animationCycle" : 1.0,
  "frameNumber" : 2,
  "power" : 3,
  "damagePoly" : [ [-5, 5], [-5, -5], [5, -5], [5, 5] ],
  "supportsProcessing" : true,
  "actionOnReap" : [
    {
      "action" : "config",
      "file" : "/projectiles/explosions/globeexplosions/magentaglobeexplosion/magentaglobeexplosion.config"
    }
  ],
  "damageKind" : "plasma"
}