Changing 'dynamic material element index' via variable on bp in level causes 'access none' error. ??

Just trying to figure out how to word this lol.

I have a tag-based ‘lightswitch grouping’ set of blueprints. One Lights_BP, and one LightSwitch_BP.

If I tag my light and it’s respective light switch ‘bathroom’ for example, it will only turn off/on the bathroom lights.

I have several different meshes to go with the lights_BP and here lies the problem: I’ve got a dynamic material instance which controls a scalar parameter for emissive on one of the materials assigned to my light. On the standard mesh this is Element 1 while on a second light mesh this is Element 3.

Inside my Lights_BP in the construction script I have a setup that exposes the Create Dynamic Material Instance Element Index to a variable I made named Material Element Index

I have this variable set to public so I can modify it in the details pane per instance in the level, but it doesn’t seem to want to cooperate. When the variable in the details pane is left at 1 everything runs fine, but the emissive appears on the wrong material.
Upon changing the variable to the proper element index for the mesh I get an accessed none error that reads:

Accessed None ‘Dynamic_MAT’ from node Set Scalar Parameter Value in graph ‘EventGraph’ in blueprint Lights_BP

Last but not least I’ve attached some reference screenshots below:

Light Mesh #1

Light Mesh #2

I fixed it.

Setting the source material was the fix (first image)