Crashing when adding a material

[astral loom]

I am making a modpack containing custom elements and materials.

For some people (and sometimes me), a crash similar to this: https://mclo.gs/1FOUbHn happens.
It is very sporadic, and specifically for me it has fixed itself.

I am unsure what could it be caused by. I have tried renaming the elements folder to !elements and aelements and tried placing "priority: 1" inside the elements files but it hasn't fixed anything.

Current folder structure in picture.

^ element registry

v material registry

[astral loom]

It might be a problem where the materials.js loads up before the other material registries

materials.js has a material modification event as well

So that might be a problem