Yep, I’m using Lumen. Both with and without Lumen brings to no change 
On a parallel discussion, I received feedback on a Niagara bug, where large world coordinates induce a reset of all Niagaras which travel “too far”.
The reasons seems to be hardware-related: current GPUs work with floats and don’t support doubles (or support them very badly).
I suspect the issue here might have a similar root cause…
Edit: link of other thread Niagara Particles Reset in Large Worlds after 5.1 update - #9 by Michael.Galetzka