Welder Sprite sticking
I've seen this happen a few times: First, my friend was playing with me while I hosted the frostbite campaign. While welding on a gird, the blue flame animation signifying that he was using the welder got stuck and duplicated multiple times every time he turned on the welder. He would move to a new point/angle and start up again and it would remain on my view. He claims he couldn't see it, so it might only be on the hosting end? after he moved the grid he was welding I was able to walk back through the floating blue flames.