I did not think it would be worth writing but then I saw the topic was alive Dec 20.
I’ve had the same issue, which brought me here. I took Hien’s advise and mixed it up a bit.
The projectile movement component is set to rotation follows velocity.
however, the actor, the niagara effect, the projectile movement, is all not set to replicate.
When I fire the function, i use multicast. This gave me a clean effect. I suppose, running your collision on server would be enough. No need to multicast