What is causing my umap assets to unload?

It seems that whenever I travel a certain distance away from the center of this map, all of the assets in the .umap cease to be rendered. I can still interact with the geometry and collisions of the assets within, but am unable to see any of them. What’s more bizarre, is that the distance traveled to replicate the issue is horizontal. I can travel upwards from the center seemingly infinitely without it happening. This effect happens when using the Play in Editor feature, but not when using the editor normally. Similarly, the effect doesn’t take place when starting play in the .umap in question, but when being placed there from another map that I’m streaming.

I have a set up with 3 .umaps streamed with each other. Two of them are very small, the other has the massive landscape with a handful of other assets, including a directional light, sky light, atmospheric fog, and Lightmass Importance Volume. When the unload happens, I can see the other two maps far below, then I can move my character back into “range” to re-load the map that I’m in. If I load the landscape map manually in the editor and use the ‘Right Click → Play from here’ feature, then this bug does not occur. It is important that these maps be streamed together, are there any clues as to what I can do to solve this?