Hmm, this is a wild guess, but I’d suspect collision shenanigans here. There was a big slowdown I had a while back where my actor was set to merge collisions (might have been instanced static mesh based, cant remember now), the merging of collisions basically made it crawl.
So its likely there’s a checkbox somewhere you havent checked, or have checked when you shouldn’t, which seems to be the way with UE 