Hey,
thanks for sharing your investigations, however I have not found a solution to this. At the moment I have those default homing projectiles, but they keep orbiting their targets for an eternity right now, which looks pretty silly when there are more than 4 projectiles at once …
It’s not THAT important for me right now though, so I’m focusing on other things and I keep hoping for someone else to struggle with this/find a solution 
Your best bet will probably be to write one from scratch though I guess. I hope you find a fitting solution 