Updating per-instance data at runtime in BPP packed level actor not working

I’m trying to update per-instance data on instanced static meshes inside a BPP packed level actor at runtime, but not having any luck. Is there something about packed level actors that prevents them from being updated after creation? I’m using “Set Custom Data Value” in my BP, and the material being updated has the PerInstanceCustomData[0] implemented and “used with Instanced Static Meshes” set to true. I can confirm that when setting the “Num Custom Data Floats” to 1 on the ISM collection that the materials do update in the editor. But at runtime I don’t see them update when a component inside the BPP fires. My guess is this has to do with the instanced static meshes being inside a packed level actor. Anyone have any suggestions?