Unfortunately you hit a known issue with the 3rd parties airports, which use same folder names for materials, leading to a CTD
You very likely have another airport with same mymaterials name somewhere
So renaming the folder as you did is fine
But you need also to update the layout.json file with the new name you assigned to the folder. Use a text editor for that
There’s also a utility that build the layout.json for you, it’s called MSFSLayoutGenerator.exe, just search the forum here aand you will find the download link
awdesigns need to update their package ASAP for this issue