I had a similar issue: I had spawn points on a moving platform that worked great in testing before publishing, but completely failed after publishing (evidently much of Fortnite ignores moving objects, unlike Unreal1 which handled it beautifully twenty years ago).
I had to write a custom device with an array of my spawn points, then whenever an actor spawned on one of those spawn points, I’d teleport them to take into account the movement of the spawn points.
Even if you do not have the exact Issue I had, you can use a custom device capturing actor spawns to print out some useful debug messages.