Component FOD / Solder balls

We are experiencing FOD coming off of a Cooper Bussman fuse. The components are dark with a metal like substance. In our testing based on what we were seeing we placed components onto a piece of FR4, placed a drop of flux onto the component and ran them through the reflow. The components came through "clean". We are trying to drive to a source of micro solder balls we are experiencing.Has anyone experienced anything similar?

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